B-Roll

Illustrative footage inserted into a broadcast news piece or interview. It is chosen to illustrate what is being said, and as a way to cover editing and continuity errors in production.

You get the idea.

The name is the actual term used by news people. It refers to the fact that this footage is usually spooled out from the second ("B") deck on a Linear Edit system. The "A roll" footage is the interview itself, the presenter's questions, and any directly documentary footage. B Roll is usually generic, and can in fact often be Stock Footage. News about financial stories tend to use the B-roll because the new labor figures aren't something you can really film, unlike people standing in a unemployment line or working in a factory. Faces are almost never shown in b-roll when the story deals with sensitive issues like child welfare, adultery, obese/fat people or any kind of sexual topic- like condoms or teen sex.

See also B Roll Rebus, where several of these shots are used in rapid succession.