Board Thread:Naruto Discussions/@comment-1251315-20140904112318/@comment-945885-20140906051152

The term OVA literally refers to direct-to-video (VHS/DVD) releases. There have been a few Naruto OVAs, but a televised episode would never be considered an OVA, let alone numbered episodes like the upcoming special (episodes 376-377).

Filler technically refers to anything that's used to pad an episode. In general media discussion, it basically encompasses anything that doesn't contribute to the overarching story.

In the anime fandom, filler is usually used to refer to original material created by the anime staff to pad episodes or seasons in order to avoid running out of source material to adapt. Usually considered to be of dubious canonicity.

In Japan, the term "anime original story" is instead used to refer to any original animated material that's not adapted from the original source material, including "filler" arcs and specials, OVAs, and movies. The term "original story" is also used for audio dramas and video games. It can refer to both canon and non-canon content.