A style of video editing in which you edit together clips in pairs - A and B - typically with a transition from one to the next. In Premiere, the A/B Editing workspace configures the Monitor window in Program view and the Timeline with separate expanded tracks for Video 1A, Video 1B, and Transitions. This style is useful for assembling a program with simple drag-and-drop convenience. You can see also single-track editing.
A-Roll and B-Roll is the most helpful when editing complex projects. Creating an edit based on your A-Roll as a first step can be pretty helpful. B-Roll is to be used either as complementary footage, or to fill in gaps which the A-Roll can’t or doesn’t do well enough.
In the digital age of filmmaking, the term A-roll has fallen out of practical use, but the meaning of B-roll remains a term filmmakers should know.