Dr. Robert Custer, MD who was the father of gambling addiction treatment, wrote that there were several classifications of gambling styles. I have added a few points to his writings as well.

Social Gamblers:

• Most people who gamble are social gamblers
• Gambling is one of many forms of entertainment they engage in, it is not their main recreational activity.
• They rarely think about gambling.
• Gambling episodes are usually infrequent, but there may be some regular activity as well (e.g., a monthly poker game, an annual vacation to a gambling destination such as Vegas, a weekly or even daily lottery ticket).  
• The Social Gambler's gambling does not result in any negative life-consequences.
  
• There is no loss of control over gambling duration, frequency or money spent, *no substantial losing single episodes. .
• They would not be upset if unable to gamble ever again.
• There are no long lasting negative financial consequences as a result of the gambling.
• *The person who is gambling and their family can safely afford the gambling (there is a saving account, there is also an emergence fund of several months expenses, no debt on credit cards, all bills paid).   
• *There are no attempts to hide any aspect of the behavior.

 Frequent Gamblers:

(also called "heavy" or "serious" gambling):

• Gambling is an important part of their lives and would missed if they could not engage in it.
• There may be an intense focus on a single form of gambling (e.g., horse racing, poker, sports betting).
• There is no loss of control over wager amount or frequency.
• No progressive increase in wager size over time.
• No financial strain due to gambling, money for retirement, family, health, etc. is not being diverted.
• Money is not borrowed from any source (including credit cards).
• Gambling is generally not viewed as a way to pay for basic life necessities or luxuries.   
• No relationship arguments or relationship problems occur due to gambling.
• Gambling does not diminish their work performance or focus.  
• Wager size is responsible and reasonable for the person's income.
• Relationships with family members and friends are not diminished due to time spent gambling.
• The time spent gambling appears reasonable to an outsider.
• The gambler does not chase losses.
• There are not mood swings associated with the wins and losses.
• The gambler remains interested in non-gambling activities and engages in them frequently.
• Non-gambling friends are plentiful.

Please note:

Problem and pathological gamblers often minimize their situation to try and appear like frequent gamblers, and a frequent gambler may be progressing into a problem gambler very very slowly.  The opposite is also possible

and

Interestingly if a gambler is affluent the distinction between frequent and problem gambling, and from problem to pathological, is much more complicated.

Problem Gamblers:   

• Gambling results at least one negative consequence to the gambler or person in their life, this would include relationship problems.
• Money used to gamble with should be otherwise allocated to other things.
  
• There might be family discord regarding the time or amount spent gambling. 
• The gambling may diminish work performance or ability to focus on work fully.
• Long term goals and ambitions are sometimes replaced by gambling.
• Usually the gambler can and does quit or stop for periods of time, and may do so to "prove" that they do not have a problem.
• Often there is some degree of intolerance to losing as demonstrated by mood swings after a loss, or chasing the loss to get even.
• Problem gamblers may deny that any problem is occurring despite the observations of others.
• There may be attempts to hide or minimize gambling behavior.
• Often thinks of gambling as a second job or a viable source of revenue; they may aspire to be professional gamblers.May try to earn money needed for daily living by gambling, and in the process get into financial jams.
• Time spent gambling exceeds what an outsider would think is reasonable.  
• Unless the gambler is affluent, money may be occasionally borrowed from other people or credit cards.  
• Problem gamblers often temporarily quit gambling after a big loss and will resume once their finances have stabilized.   
• Often viewed as being a "regular" at gambling establishments, staff may know their name and they receive comps, these comps, or other reward programs foster more gambling.  
• The severity of the problem does not meet the full criteria for a diagnosis of pathological gambling as defined in the Diagnostic and Statistical Manual of Psychiatry, DSM-IV™ (a copy is provided in the assessment section) but they often have between 1 and 3 symptoms.

Pathological Gamblers (also called Compulsive Gamblers): 

• usually not reversable into lesser gambling styles, the old saying goes once a cucember turns into a pickle... move this down
  
• This is the only "type" of gambler that has been fully defined by the American Psychiatric Association as a mental disorder.
• Usually has had at least one financial bailout from a friend, family member, maxed out credit cards or taken out loans from financial institution,  unless they are affluent, although some pathological gamblers never have had a bailout.
• Pathological gamblers share some of the symptoms that are evidenced in problem gamblers (see above list).
• There may be attempts to justify, rationalize, hide, and/or minimize their behavior to others.
• Often they will mis-conceptualize the gambling problem as a financial problem.
• May blame others for stress they are creating.  
• May try to win money needed for basic living expenses.  
• Winning means more time to gambling, wins are usually "re-invested" into more gambling.
• Usually thinks that they are only hurting themselves, unaware of the impact of their gambling on others.
  
• Wager size increases over time (measured usually in years).
• Uses money to gamble that should otherwise be allocated/invested; for example does not have a independent retirement plan (e.g., IRA) that not associated with their work plan (e.g., 401K).  This would not apply to some people.
• Gambling does not have to be daily in order for it to be pathological.
• Engages in "creative financing" by obtaining loans and credit.
• May have burned out relationships due to gambling and borrowing.   
• Unable to easily quit gambling for long periods of time.  
• May promise self or other to quit gambling after a large loss or win, but can't or doesn't for long.
• May feel urges and cravings to go gamble.
• Frequent fights with spouse/partner, blames them for the problems.
• Feels excited when gambling or about to gamble, might have a rush just walking into gambling establishment.
  
• Gambling establishments may feel like "coming home" when they enter after an absence.
• Other gambling patrons or more likely casino staff are thought of as "friends" despite a lack of connection outside of the gambling venue, although this is not very common.
• The solution to financial problems and stress created by gambling is to gamble more in order to finally hit a big win, or at least recover losses.  Thus the problem also is seen as the solution, a characteristic of addiction.  
• A Pathological gambler meets the criteria for the disorder as listed in the as defined in the Diagnostic and Statistical Manual of Psychiatry, DSM-IV™ (a copy is provided in the assessment section).
  
• I have had many severely disordered gamblers that would adamantly state that they are not compulsive or pathological.

Professional Gambler: 

• Rarely loses control when placing bets. 
• Gambling is methodical and planned (e.g., a professional horse gambler may not bet on every race).  
• Maintain discipline and refrain from impulsive betting 
• Accept financial losses without chasing to win them back.
• Professional gamblers do not meet the DSM-IV criteria for pathological gambling, but may have a couple of symptoms (e.g. preoccupation). 
• Gambling is their primary source of income. 
  
• Most problem and pathological gamblers fantasize about being a professional gambler or mistakenly believe that they are, there are very few true professional gamblers.
• Many professional gamblers will eventually evolve in to problem or pathological gambling.  
• It has been estimated that there are fewer than 3,000 professional gamblers in the US and Canada and only 50 professional gamblers in the U.S. who earn over $100,000 dollars annually by gambling.  Psychological profiles of professional horse gamblers showed they tend to be somewhat boring, socially insensitive, extremely unsentimental, hyper-vigilant, and very tense. (McCown & Chamberlain, 2000).  
• The term "professional gambler" is very complex in distinguishing from problem and pathological gambler and the assessment should be conducted by a trained professional therapist who also consults with the gambler's family/friends regarding the presence of symptoms.
• My personal view is that there is no such thing as a professional slot machine player, roulette, baccarat, or most other forms of gambling. Poker is a clear exception, HOWEVER sports betting is not clear and sports betting professionals are extremely rare (other than the bookies and odds makers) and would probably require a large team of people to pull it off.. as would blackjack card counting teams (ala MIT) (and which is where most of the want-to be professionals that I have seen have done the most damage to themselves).
  

Action Gambler:

• A win creates a "rush" that is probably associated with an excessive release of the neurotransmitter dopamine.  Dopamine is a brain chemical associated with the subjective experience of pleasure.    
• Reacts to gambling with an unusual degree of excitement, although this may experienced by the gambler but not expressed.  
• More often plays games such as cards, craps, roulette, sports betting.
• A win may lead to larger bets.
• Gambling excitement is extremely pleasurable and achieving it becomes a major focus in the gambler's life.
• More men are action gamblers than women  
• Often associated with ambitious, high intelligence, Type-A, "driven to succeed" personality traits. 
• Besides gambling in a habitual pattern, they are more likely than the escape gambler to bet when feeling good, happy or lucky.
  
• 
  
• 
  Escape Gambler:  
• Besides any habitual gambling patterns, they are more likely to gamble at times to escape emotional pain and life problems. 
• Gambling produces a numb, trance-like, state of consciousness where problems are not in awareness. 
• Slot machines and video poker are the most common forms for these gamblers. 
• After many years of gambling action gamblers often start to experience escape-style gambling.
• Increased chance that an escape gambler has been physically or emotionally abused.
  
• Women are more often then men to be escape gamblers.
• Antisocial Gambler: 
• Engages in criminal activities, scams and rip-offs.
• Gambling is a method to steal money, may use loaded dice, marked cards, and fixed sports events or horse races.
• Different from gamblers who commit a crime to pay debt.
• May have a diagnosis of Antisocial Personality Disorder

• 
  Binge Gambler: 
• Frequency of gambling episodes are periodic rather than consistent
  
• Long periods of no gambling are followed by binges that can be very costly financially, emotionally and damaging to relationships.
• There is an illusion of being in control that is a function of the ability have extended periods of not gambling.
• The relapse cycle is often triggered by a perceived "surplus" of money, while the binge cycle typically ends after a huge loss.