I just realized that many newbies into any sort of fandom might not know the words "canon" or "fanon" either.
Canon - events that happened on air in the show. Applies to character traits as well, but there are of course some interpretations to those that has be taken into account.
Fanon - Events or any stuff that has become a "fandom myth" concerning the show. This is stuff that, for example, becomes very common in fanfic that after a while almost everybody sort of adopts it like canon when in reality it's not.