Timeline track

Video tracks follow one rule: whatever sits on a higher track covers what is below it, unless you make it transparent, shrink it or blend it. Lower thirds, overlays, B-roll and picture-in-picture all rely on that. Audio behaves differently, since every audio track sounds at once and sums together, so stacking dialogue, music and effects is normal rather than a conflict to resolve. Most editors settle on a convention early, dialogue on one track, music on another, effects and room tone below those, because it makes muting and level changes painless. Premiere and Resolve call them tracks; After Effects and most motion tools call them layers.