Groups function like a mini chatroom or notice board (or a social media "wall") where members who have joined can comment and post.
You can create a group by clicking the user menu which can be accessed by clicking on the "person" button at the top right hand corner of the page. If you have uploaded a profile photo and it has been approved, then simply click your profile photo button at the top right hand side of the page. You will then be presented with a menu - simply click the "My Groups" button. Once you have done this simply follow the instructions.