The user lays a trap of levitating stones around the opponent's team. The trap hurts opponents that switch into battle.
Stealth Rock's damaging methods are rather unique. Instead of doing a set amount of damage for the amount of layers given, it instead is based on the opponent's type. The attack is a Rock Type attack so the damage is based upon the opponent's Weakness to it. For a full chart, click here
1/32 of Max HP (3.125%)
1/16 of Max HP (6.25%)
1/8 of Max HP (12.5%)
1/4 of Max HP (25%)
1/2 of Max HP (50%)
This shows that Stealth Rock can easily help defeat the opponent with little effort if they use a Pokémon such as Charizard or Articuno