How this Chart Works:

When a Pokémon type on the right
attacks a Pokémon type on the left, the symbol shows how
well it will do. Lets take Squirtle's Water Gun and
Charmander for example. Water gun is a water attack, so
that would be #3, and Charmander is fire, #2. So first we
look at the left hand side and find 3, then we keep going
to the right to find 2. There's a green circle there. We
check the legend, and it means Great. So, Water Gun will
be Super Effective against Charmander.