In Shooter the players fight with weapons versus their friends in multiplayer mode or they fight versus enemies which are played by the computer.
There are two different forms of shooter:

Ego-Shooter:

In ego-shooters the players see the world and their enemies with the eyes of their characters. Ego-shooters are often only allowed for people over the age of 18.

Third-Person-Shooter:

In a Third-Person-Shooter the players see their character with the eyes of a third person, which walks direct behind the character. But the rest is the same like an Ego-Shooter. They are often also allowed for people over the age of 18 or sometimes 16.