Immunity

Full effect

This Pokémon cannot be poisoned. This includes bad poison. If a Pokémon is poisoned and acquires this ability, its poison is healed; this includes when regaining a lost ability upon leaving battle.

In game description

The Pokémon's immune system prevents it from being poisoned.

Using Immunity in Cobblemon

Abilities are passive and always active, so Immunity costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.

See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.