What is B-roll?
B-roll is supplementary footage cut over or between your main shots, used to illustrate what you are saying and to hide edits in the primary camera angle.
Updated · Editorial policy
The main footage of you talking to camera is the A-roll. Anything else on the timeline, such as screen captures, product close-ups, archival clips or stock shots, is B-roll. It usually sits on a video track above the A-roll with the original audio still playing underneath.
B-roll decides whether a talking-head video is watchable past the first minute. It also changes what you shoot: if you know a two-minute explanation needs visual support, you grab the close-ups on the same day rather than discovering the gap in the edit and having to re-shoot or rewrite the script.
A practical habit is to mark your script where the viewer needs to see something, then shoot each of those as a four-to-six second clip with a small amount of movement. Shoot more than you think you need, since a clip that looked fine on the camera screen often turns out soft or badly exposed once it is on a big timeline.
Where B-roll shows up
You will meet B-roll most often while comparing video editing saas - Descript, VEED, Kapwing, and InVideo all deal with it, though not in the same way or at the same price.
Related terms: Chapter Markers, Jump Cut, Safe Zones, and Video Transcoding.