Oh, that's simple, really! Teams are made for helping team members out, like helping with different strategies of battling, and a bunch of other great things like that! Some teams have different goals from others, like Nova is an all around competitive battling team with high standards, while teams like Quasar are there to help you improve or just to be active in a Team. Also, there are great things like Team Wars, where teams go head to head in Poke Battles, and there are a bunch of other great things like discounts in different shops and such. If you want more info., try talking to a team member of the different groups to see which one is right for you!~