Wiktionary
n. The creation of fanvids.
Wikipedia
Vidding is the fan labor practice in media fandom of creating music videos from the footage of one or more visual media sources, thereby exploring the source itself in a new way. The creator may explore a single character, support a particular romantic pairing between characters, criticize or celebrate the original text, or point out an aspect of the TV show or film that they find under-appreciated which is commonly uploaded to a variety of social media outlets, the more popular being YouTube. The creators refer to themselves as "vidders", their product as "vids", "fanvids", "songvids" or the more recently adopted name "edits" and the act itself as vidding.
Vidding can occur within a fandom; however, it is also often considered its own fandom, as vidding fans will often watch vids simply because they are vids. (This is distinct from fan fiction readers and other fans, for instance, who tend to choose what to engage based on source text more than form.) Accordingly, vidding has its own dedicated fan convention, Vividcon.
Fan videos within the world of anime fandom are distinct from the videos created by vidders. A fan-made music video using anime footage fans is called an anime music video or AMV, not a fanvid. While a large number of anime video makers are male, the bulk of vidders in media fandom are women.