A-B Split

A-B Rolling was actually a thing in the movie biz. There was the primary action with the big star, but the director didn't quite get the linear action camera placement right, so he'd cut away to a B-Roll. Think: slow motion zebra running from hungry capitalist lion. Sometimes the B-Rolls were more interesting to watch than the "A" action, and thus was born A-B Rolling, which then took on a kind of mini-industry of its own.

The most prolific use of A-B Rolling today lives in digital marketing, where the creative content...think: banner ad...seeks to get clicks. One creative shows a scantily clad Democrat, another shows a Republican in Burberry. One is the "A," the other is the "B"...and their effectiveness in drawing clicks is tested against the constituency to which they are distributed. Winner gets...more distribution.