Board Thread:Theories and Speculation/@comment-1512913-20190615111653/@comment-3279282-20190616153309

Filler - Anime content that does not adapt the manga's main plot. It's used to allow the mangaka to produce more manga content. Although the terms are often used interchangeably, filler does not necessarily mean anime-only or non-canon. Example: Kakashi Gaiden.

Anime-only - Anime content that wasn't adapted from any kind of source material (aside from the overall series, characters, plot etc.). It can range from extra scenes to whole arcs and is often used as filler material, to stretch out episodes and such. It's considered to be non-canon by most, although cases exist where an author has connected both anime-only plot and manga plot. Example: Borutos Yagura arc, and thus the entire anime, was connected to the manga by an author statement.

Canon - There's no set definition for the word, I think. It could probably be seen as another word for "official". This word is a Western invention and does not exist in Japan. Depending on a fan's opinion, what is and isn't canon is subject to change. My own definition is "The original source material of a series dictates the canon, all adaptions are non-canon to the source material. This can only be overwritten by author statements." Of course cases like Pokémon exist, where the anime tells an entirely different story than the manga or even the games. For Naruto, the manga and the databooks are canon, for Boruto, the manga, databooks and the anime are canon, because of the aforementioned author statement.

From what I know, Japanese people don't care too much about what's canon and what isn't. They simply take the series at face value and don't bother with inconsistencies. We all could learn a lot from that mindset, although it's not really helpful for handling wiki content.