It's a group of people who are just plain awesome.
They can be brought together by many a-ways, but the best Awesome Foursome are brought together by a socially unacceptable (but still pretty damn cool) past-time, such as Explorers in Britain.
This can feature other people.
Lucy : Heyy
Ali : Heyy
Fletch : Heyy
Lily : It's the Awesome Foursome!!
Kyla : Heyy
Lily : ... Feat. Kyla!!