Friendship Groups:

Friendship groups (commonly found in schools: in particular girls) are groups of friends you hang out with and play/talk with; often of which represent a group who balance each other out in a range of characters. Not everyone has a paticular friendship group, some people prefer to move from group to group, or have one or two best friends.
Personally, I think finding the right friendship group who accept you and share your values is not always easy, but is incredibly important. Being part of a particular group shows you support them and what they stand for, and that you're prepared to be there for each other.