From Halopedia, the Halo wiki
ViDocs are video documentaries created and released by Bungie and later by 343 Industries and Ensemble Studios. These videos give players insight into the creative development processes involved in the progress of the games and other media, and usually contain interviews of various developers working on the game in question as well as game footage. Contrary to popular belief, ViDoc does not actually stand for "video documentary"; it is a Bungie-created combination of the words "visual", "informational", and "documentation".
The first ViDocs were produced by Bungie for Halo 3. These ViDocs ran for roughly seven minutes (except for Journey's End), and had titles in Latin that were somehow relevant to the content of the videos. Other ViDocs reference famous quotes, such as "Once More Unto the Breach" and "On the Seven7th Day...".
343 Industries initially labeled their development documentaries Behind the Scenes or BTS as an alternative to "ViDoc", though they have since adopted the latter term. Halo 4 had its own series of video documentaries called Making Halo 4, Halo 5: Guardians had a subseries called The Sprint, while Halo 2: Anniversary had its own documentary movie called Remaking the Legend instead of a short series of videos.
Halo 3: ODST
Halo: Combat Evolved Anniversary
Halo 2: Anniversary
Halo 5: Guardians
The Sprint series
Halo Wars 2
Halo: Fireteam Raven