B-roll
Supplementary footage cut over the main track: for cover, pace, and showing what's described.
B-roll is everything that isn't the primary take: the product on the bench, hands working, the wide of the room, the street outside. It's cut over dialogue or narration.
It does three jobs at once. It shows what's being talked about, which is almost always more persuasive than hearing it. It hides edits in the main take, so you can cut a rambling answer into a tight one without a visible jump. And it controls pace: a piece with no b-roll feels static regardless of how good the talking is.
It is also the single most common thing missing when an edit comes back thin. Shot lists routinely under-specify it, and a crew that has wrapped can't go back for the shot you didn't ask for. Ask for more than you think you need, and name specific shots rather than writing "b-roll".
Where this comes up
Build it in edit order to catch what's missing, shoot it in setup order to save hours, and never write the words "b-roll" on it.
Brief first, shortlist second, price last. How to run a hire that gets you the film you wanted instead of the cheapest version of something adjacent.