Fanfictions (Canon)
The fanfiction does not break anything established as canon.
This could offer insight to what went on behind the scenes.
This should use only canon tribes.
Fanfictions (Semi-Canon)
The fanfiction may break some established canon, but does not use fanon tribes.
Shipfics between canon couples is often a good example.
Fanfictions (Fanon)
This fanfiction may use fanon tribes, settings, or alternate universes.