There are several footbag disciplines. The two most imprtant of which are freestyle and net. On top of that, there are the precursory discipline of circle kicking (including more advanced varieties such as foursquares) and footbag golf.
These disciplines are very different in practice. What unites them is the playing equipment: a footbag. You can acquaint yourself with the different disciplines that have originated from kicking this little ball in the subpages.