In film, that's where a director shoots a portion of a proposed movie to demonstrate their ability and style in shooting a film.
Well, on my films I'm always guaranteed the role of director! However, those who've been long time supporters know I always shoot my films entirely, days before the actors arrive, to make sure everything will work out.
I don't have long shooting schedules, almost never do reshoots, and so I have one opportunity to get it right. I make sure I know how the film will look before I bring everyone by, and that way the shoot moves like clockwork (assuming the clock is slightly broken).
So, I'm going to assemble one of my personal 'proof of concept' shoots with no actors, and present it to you. An interesting look at what my process is. I should have that up for you in a day or so.
And when the film comes out down the line, I'll add it to the BTS.