Timeline Tracks
On the Timeline, you can arrange your media to create and edit your video.Only media on the Timeline will be rendered as a video.
Caption Track: All captions that you add via the Captions pane will appear on the Captions Track. Move the captions to the location you desire by selecting and dragging.
Video Track: All video that you add to the Timeline will appear on the Video Track. Move the videos around on the Video Track by selecting and dragging.
Audio Track: All audio that you add to the Timeline will appear on the Audio Track. Move the audio clips around on the Audio Track by selecting and dragging.
Locking:
You can lock any track to prevent editing or other changes being made to the media on it by pressing the Lock button. To unlock
the track, press the Lock button again.