it's when there's a lot of damage,for example a water type against a fire type
dragon and ice is most efective against dragon.
Steel is super effective against rock type pokemon.
ground type Pokemon are super effective against poison type Pokemon.
Ghost and Dark attacks are super effective against Ghost type pokemon.
Rock, electric and ice are super effective against flying type pokemon.
Yes, Ghost type is supper-effective against Psychic and other Ghosts.
Water and Grass attacks are super effective against Onix.
There are three types that are super effective against psychc pokemon. They are Dark, Ghost, and Bug. If you need any other information type in psychc types on Wiki
normal type Pokemon are not super effective against any type.
Phycic pkm are super effective against fighting pkm. and flying larson
using super effective Pokemon against his' Pokemon you'll need a super effective Pokemon against his starter but you don't need to win with super effective Pokemon just stock up on potions that's what I do.
In Generation 1 (Red, Blue, Yellow) Bug is super-effective against Poison, and Poison is super-effective against Bug. Weedle Kakuna Beedrill Venonat Venomoth