According to wikipedia:
A gamer (gamer in meaning in English) is the term used in the Spanish language to define the type of gamers that are characterized by playing with great commitment and interest and have a diverse range of knowledge about video games. To refer to this concept in English we use the term hardcore gamer. Put more simply, a gamer is someone who is dedicated to the games a lot of hours (playing and reports), or daily, a "viciae.
Description:
The gamer is a gamer who has great passion and interest in play and know about video games and their main interest, besides enjoying the game, is finish high records and make full use of the same, making it different, the so-called casual gamer, which just playing to play or to spend a fun time without major goals, in some cases trying to end the game.
Differences with the casual gamer:
gamer is different from the casual gamer, casual gamer in that generally prefers the game console or cheaper, easier to use and play, or simply that it is fashionable. Usually there is little knowledge about construction, quality, and other more specific issues of video games.

The casual player does not have the "gamer culture" that is, knowing what is a texture, Video Card, etc.., And therefore does not care or bother to install it, looking at the best only in the graphic quality and popularity. Casual players also fail to appreciate the graphics to specify that define the game as the HDR, shading or other new inclusions computer and therefore never come to understand what is or is interested in knowing.

In contrast to the gamer usually not interested in "casual game" and is mainly concerned with more complex games that are difficult to manage and dominate, they really present a challenge, never mind spending hours and hours practicing to learn and operate all aspects hidden game, dominating and interested in more specific terms and topics as related to graphics, computer, hardware, etc., and it is present and properly used the best technology developments to create the video game industry. Also the gamer is interested in the multiplayer games or online games, and if you can create clans or participate in tournaments to show their abilities. For many, being a gamer is a lifestyle.

These features make the gamer to be considered a kind of geek (geek video game), hence the term gamer is also used to indicate the fanatical gamer, but often there are big differences between the gamer and the rest of the geek community. Some gamers may suffer cyberaddiction for video games.