What is the difference between a first-person shooter and a third-person shooter?

In a first person shooter a player sees through the eyes of his avatar. In a third person shooter a player sees through a camera over the top of his avatar.

In some games, you play from over the top of the character (3rd Person), and then when you sight down your weapon zoom into the characters eyes (1st Person). This can also reverse as in Halo where you spend the majority of your time in first person until you enter a vehicle and gain a third person perspective.

First and third person also have some variations:

• In some first person views, you can see your avatar's arms and feet when you look around, while others do not.

• Two main variations in third person views exist. The position of the camera; over head, over the top, over the shoulder, etc. and the cameras mobility; stuck in position, or rotatable around the character.

Games can be both first- and third- person.

In Halo the game is mainly played in first person, but when you drive a vehicle it goes into third person.

In the Burnout series of games the cars can be driven in first or third person mode. (Not strictly a shooter, but the point remains).

Oddworld: Stranger's Wrath is mainly third person, but you can choose to go into first person at virtually any time.

A lot of Nintendo games (some Mario titles and the Zelda Wii games spring to mind) are basically third person but allow you to switch to first person to look around (but not necessarily move).