B-roll footage and how it works

B-roll footage refer to the  alternative footage intercut with the main shot in an interview or documentary,in order to illustrate the story fully and stay attract viewer's eyes. So B-roll is definetely a big deal. 

To shoot a B-roll footage is slight different from main shooting. For instance: blur for focus, add different angles and so on, Due to B-roll footage will go over audio, so it gives filmmakers more room too be creative and chance to go back do it again.