Inner Focus

In battle
Inner Focus prevents the Pokémon from flinching. However, Pokémon with this Ability can still flinch to a Pokémon with Mold Breaker, Teravolt or Turboblaze.

While some descriptions state that the user flinches, Focus Punch failing due to taking damage is not flinching, so the move is unaffected by Inner Focus.

If the Pokémon is hit by a move that always causes flinching, the message "'s Inner Focus prevents flinching!" (Generation III) or " won't flinch because of its Inner Focus!" (Generation IV) will appear.

Outside of battle
Inner Focus has no effect outside of battle.

Pokémon with Inner Focus
Source- https://bulbapedia.bulbagarden.net/wiki/Inner_Focus_(Ability)