Pokemon Types

Well, beside HP and CP, you should know well the types of your pokemon and your enemy's pokemon, because some types are only effective against several types. So, watch carefully and make sure to know the enemy's pokemon types before battling them!

Effective Against: Steel, Bug, Ice, Grass
Weak Against: Rock, Water, Ground

Effective Against: Fire, Ground, Rock
Weak Against: Electric, Grass

Effective Against: Water, Ground Rock
Weak Against: Fire, Ice, Poison, Flying, Bug

Effective Against: Water, Flying
Weak Against: Ground

Effective Against: None
Weak Against: Fighting

Effective Against: Grass, Ground, Flying, Dragon
Weak Against: Fire, Fighting, Rock, Steel

Effective Against: Grass, Fairy
Weak Against: Ground, Psychic

Effective Against: Normal, Ice, Rock, Steel
Weak Against: Flying, Psychic, Fairy

Effective Against: Fire, Electric, Poison, Rock, Steel
Weak Against: Water, Grass, Ice

Effective Against: Fire, Ice, Flying, Bug
Weak Against: Water, Grass, Fighting, Ground, Steel

Effective Against: Fighting, Poison
Weak Against: Bug, Ghost

Effective Against: Grass, Psychic
Weak Against: Fire, Flying, Rock

Effective Against: Grass, Fighting, Bug
Weak Against: Electric, Ice, Rock

Effective Against: Dragon
Weak Against: Ice, Dragon, Fairy

Effective Against: Fighting, Dragon
Weak Against: Poison, Steel

Effective Against: Psychic, Ghost
Weak Against: Ghost

So that's all the strengths and weaknesses off all pokemon types in Pokemon Go

Make sure you remember all of it, especially when you want to take a gym!

Good Luck!