In the wild it is "eat or be eaten" and in Asteroids it is "destroy or be destroyed". Your aim is to blow the Asteroids into smal enough pieces that they can not harm your spaceship.
You need to move around the screen to avoid some of the Asteroids and then quickly go over into destroying them to survive.
The controls for Asteroids are:
Turn Ship: Left/Right arrow keys
Thrust: Up arrow key
Brakes: Down arrow key
Shoot first and then ask questings in Asteroids as that is the only way to survive