Formation

Formation is found by clicking the rectangle with red and yellow dots on it, located next to your first Pokémon in the top left corner. It allows you to change the layout of your Pokémon and choose a type, which you can level up using Formation Books (books of the same type give the most exp towards leveling it up). Formation gives stat changes depending on the type you have chosen, and this is also how the weather displayed on the top right of the screen affects your team and their damage output.

There is also a Counter tab, where you can see other Formations, whether you counter them, or whether they counter you. This will give a plus or minus 10% in damage depending on who counters who.