Supplementary footage layered over the main shot (A-roll) to illustrate a point, hide cuts, or maintain visual interest.
B-roll is everything that isn't the primary speaker shot. In a talking-head video, A-roll is the face on camera; B-roll is the laptop close-up, the product shot, the city skyline, the screen recording. B-roll serves three jobs: illustrate what the narrator is saying, hide jump cuts, and add visual variety so the brain doesn't tune out the static shot.
Tutorial videos lean heavily on B-roll (screen captures, product close-ups). Vlogs use B-roll for travel and lifestyle shots. Podcast clips use B-roll to hide unflattering frames or to illustrate references the host makes.
Kompozy's Persona Shorts can auto-pull Pexels B-roll based on keywords extracted from the script — search "modern office, laptop, coffee" and the worker downloads matching stock clips, then ffmpeg overlays them at the moments the script references them.