Platform game, or platformer, is a computer and video game genres|video game genre characterized by the character having to climb up and down, or jump from and to, platforms and ledges, while fighting enemies and collecting objects required to complete the game.
Often, the player has the ability to gain powers or weapons, called power-ups. Generally, platform games, due to their unrealistic nature, have cartoon-like computer graphics|graphics. Characters in platform games are usually based on legendary creature|legendary creatures (e.g. dragons and goblins) or anthropomorphism|anthropomorphic animals (e.g. a gorilla who rolls barrels).
Platform games originated in the early 1980s and made the transition to 3D computer graphics|3D in the mid-1990s. Sometime after the genre's inception, the term came to describe games where jumping puzzle|jumping on platforms, as opposed to shooting, was the main gameplay focus. However, many platform games feature projectile weapons, including the Mario and Castlevania franchises.
Source WikiPedia: http://en.wikipedia.org/wiki/Platform_game