If you're hosting a large meeting or group session, and you want your meeting participants to form smaller groups, you can use the Breakout Rooms feature in Teams. This will automatically divide participants up into equal groups, without them having to leave your meeting.
First of all, start your meeting. There is a button along the top of the window labelled Rooms.
Clicking this will open a menu, allowing you to customise your breakout rooms. You can select how many rooms you'd like to use, up to a maximum of 50. Teams will automatically put people in rooms and balance it out for you, but if you prefer, you can manually decide who goes into each room.
If you choose Automatically, users will be sent to rooms once they're created. Selecting Manually will mean you'll need to assign each individual person to a room. In either case, you'll be presented with a menu that looks similar to this, from which you can control, rename, and move people between rooms.
When you've finished with the breakout rooms, click the dustbin icon to remove all rooms. This will automatically bring participants back into your meeting.