The camera follows the player's avatar or other game entity, either residing within the avatar/entity, or following it from an external perspective. Cameras residing within a player avatar are frequently used in first person shooters, the camera looking out through the avatar's face. Cameras following a player avatar often appear in platform and action games. Cameras bound to non-player entities often appear in sports games, where the camera targets the play ball.
When the camera targets a player avatar, this binding affords the player a degree of control over the camera in that by moving their avatar around, players can view different parts of the game world, or view already seen locations from a different angle. When the camera targets a ball or similar game entity, the player often has indirect control over the camera through the control he exerts over the entity through game entities/avatars within his control. (One can move the camera in a soccer game by kicking the ball to the other side of the field.)
Strong example During the game action, the camera in Jak & Daxter [Naughty-Dog, 2001] follows Jak & Daxter as they move around the game world, keeping them essentially at the center of the view.
Strong example The camera in Return to Castle Wolfenstein [Markham, 2001] resides in the player avatar's head, providing a view of the game world through the eyes of that avatar.
Strong example FIFA 2004 [Harrison, 2003] centers the game view on the game ball, having the camera move to follow players that possess the ball or the ball itself. Only when the ball goes out of the play field does the camera stop keying on the ball or the game entity that possesses it.
Harrison, B. (2003). FIFA Soccer 2004. Electronic Arts, playstation 2 edition.
Markham, D. (2001). Return to Castle Wolfenstein. Activision Publishing, Inc., windows edition.
Naughty Dog, developer (2001). Jak and Daxter: The Precursor Legacy. Sony Computer Entertainment America, playstation 2 edition.