You have the survival mode where the goal is to survive. As long as possible.
You have a standard handgun and you can buy new weapons.
There are more than 15 different weapons, but you can't find them all, you can buy them at a random crate.
Beware of the different types of zombies, some are very fast or very strong.
If that's not enough, there's the multiplayer.
Where you can shoot at each other and make as many kills.
In multiplayer mode not all weapons are available.