STAB (stands for Same-type attack bonus) is a boost in the base power of a move that has the same type as the Pokémon using the move. This boost increases the damage done by 50%. This boost can become 100% instead when a Pokémon has Adaptability as its natural Ability.
For example, a Fire-type Pokémon using a Fire-type move will gain a 50% boost in power for that turn, because the attack is the same type as the Pokémon. STAB does not apply to moves that do a set amount of damage, nor ones that do not use the normal damage formula, such as Dragon Rage and Seismic Toss.
Misconceptions[]
Hidden Power[]
It is possible to receive same-type attack bonus with Hidden Power. So a Flying-type Pokemon using Hidden Power Flying will receive a same-type attack bonus. However, since Hidden Power can never be Normal-type, it is impossible for a pure Normal-type Pokémon to receive STAB when using Hidden Power.
Normal-type Pokémon[]
Normal-type Pokémon also receive STAB, contrary to some of the official Pokémon strategy guides.
Dual-type Pokémon[]
Dual-type Pokémon also receive STAB if the type of the move they are using is the same to one of their types. Therefore, a Pidgey will receive a same-type attack bonus from both Flying-moves and Normal-moves.