Teams are groups of users that can have up to 50 members. You can find them in the fourth icon of the game's lower bar.
There are different ways of joining a team. Once you access the tab, you will find a search tool in which you will be able to enter the name or code of the team you wish to join.
You'll also see a list of teams looking for players and you'll be able to join the one you want. You will be able to see the team's name and the number of members it already has.
Lastly, you'll be able to create your own team. Once you choose that option you'll have to enter the name, emblem, add a description and choose the type of team and its location.
Once you're part of a team, you'll be able to see its members ranked by their level and connection status, that is, if they are online or offline.
If you wish to leave the team, you'll have to tap on "About the team" at the bottom of the screen and then tap on "Leave team".