Shamelessly stolen from Wikipedia:
Historically, the term "gamer" usually referred to someone who played role-playing games or wargames. More recently, however, the term has grown to include players of video games. While the term nominally includes those who do not necessarily consider themselves to be gamers (i.e., casual gamers), it is commonly used to identify those who spend much of their leisure time playing or learning about different games.
Casual Gamer:
The casual gamer is a person who plays games designed for ease of gameplay (such as Tetris) and doesn't spend much time playing computer games. The genres that casual gamers play vary, and they might not own a specific video game console to play their games.
Hardcore gamer:
A person who spends much of their leisure time playing games. As a consequence of the large amount of time spent, these gamers often become very proficient at playing games. There are many subtypes of hardcore gamers based on the style of game, gameplay preference, hardware platform, and other preferences.
Cyberathlete:
A professional gamer (often abbreviated "pro gamer" or just "pro") that plays games for money. (The term electronic sports is used to describe the play of video games as a professional sport.) Whether a cyberathlete is a subtype of the hardcore gamer largely depends on the degree to which a cyberathlete is financially dependent upon the income derived from gaming. So far as a cyberathlete is financially dependent upon gaming, the time spent playing is no longer "leisure" time.
Historically, the term "gamer" usually referred to someone who played role-playing games or wargames. More recently, however, the term has grown to include players of video games. While the term nominally includes those who do not necessarily consider themselves to be gamers (i.e., casual gamers), it is commonly used to identify those who spend much of their leisure time playing or learning about different games.
Casual Gamer:
The casual gamer is a person who plays games designed for ease of gameplay (such as Tetris) and doesn't spend much time playing computer games. The genres that casual gamers play vary, and they might not own a specific video game console to play their games.
Hardcore gamer:
A person who spends much of their leisure time playing games. As a consequence of the large amount of time spent, these gamers often become very proficient at playing games. There are many subtypes of hardcore gamers based on the style of game, gameplay preference, hardware platform, and other preferences.
Cyberathlete:
A professional gamer (often abbreviated "pro gamer" or just "pro") that plays games for money. (The term electronic sports is used to describe the play of video games as a professional sport.) Whether a cyberathlete is a subtype of the hardcore gamer largely depends on the degree to which a cyberathlete is financially dependent upon the income derived from gaming. So far as a cyberathlete is financially dependent upon gaming, the time spent playing is no longer "leisure" time.