Different types have different effects on others. For example, the Psychic type is weak against Bug, Dark and Ghost types. However, have you ever thought why?
Here is the place to discuss reasons.
Type chart - Bulbapedia, the community-driven Pokémon encyclopedia
Use the images here to work out which are which.
I'll start with a few that I know, and some I don't.
Psychic is weak to 3 types: Bug, Ghost and Dark. Psychic is based on the human psyche; and the 3 most common human fears are Spiders (Bug), the Dark (Dark) and Paranormal activities (Ghost). Psychic is super-effective on two types, Fighting and Poison. Fighting stems from the phrases Brain vs Brawn and The Pen is mightier than the sword, all which say that fighting is not as good as thinking. Poisons are generally treated by using brains to work out cures, so it makes it stronger.
Grass types are simple. They are weak to Flying and Bug, as Birds and insects often eat plant matter. Poison, Fire and Ice are also used to kill plants. Grass is strong against rock and ground types as plant roots burrow into both the ground and rocks, sometimes breaking them. Grass is also strong against water, as water helps plants to grow.
Some things I don't get. Why is Rock strong against Flying, Bug, Fire and Ice types? Why are Ghost types weak to Ghost type moves?
Feel free to explain any type matchups you know, and ask any you don't understand.
Here is the place to discuss reasons.
Type chart - Bulbapedia, the community-driven Pokémon encyclopedia
Use the images here to work out which are which.
I'll start with a few that I know, and some I don't.
Psychic is weak to 3 types: Bug, Ghost and Dark. Psychic is based on the human psyche; and the 3 most common human fears are Spiders (Bug), the Dark (Dark) and Paranormal activities (Ghost). Psychic is super-effective on two types, Fighting and Poison. Fighting stems from the phrases Brain vs Brawn and The Pen is mightier than the sword, all which say that fighting is not as good as thinking. Poisons are generally treated by using brains to work out cures, so it makes it stronger.
Grass types are simple. They are weak to Flying and Bug, as Birds and insects often eat plant matter. Poison, Fire and Ice are also used to kill plants. Grass is strong against rock and ground types as plant roots burrow into both the ground and rocks, sometimes breaking them. Grass is also strong against water, as water helps plants to grow.
Some things I don't get. Why is Rock strong against Flying, Bug, Fire and Ice types? Why are Ghost types weak to Ghost type moves?
Feel free to explain any type matchups you know, and ask any you don't understand.