Understanding cutaways
A cutaway is the term for video placed above the main story to hide edits underneath. While a person in a video probably said the words they appeared to, they probably didn't manage to say them all in the right order, without interruptions. Removing the ums, ahs, and pauses leaves visible jump cuts: two sequential shots with almost, but not quite, the same content. To hide the edits, an editor places a cutaway above the Primary Storyline, and while you still hear the words below, you don't see the jump cut.
How does the editor find the right clip to "cut away" to? Usually, they use B-roll that's related to the current topic. An edit has to feel justified, so you can't just put any old clip on top. This is why editors want relevant B-roll; if you don't have enough, you won't be able to cover all of the edits you want to.
Not all cutaways are B-roll, though. You might cut away to a reaction shot such as an interviewer...
