Hi VideoEditor, and welcome to this forum.
Having a number of tracks allow you to switch between them and yet keep organized.
Moving clips, stills, titles /text, picture-in-picture (pip), audio "shot" along with your
camera, music, narration (voice-over) a.s.o.
If you edit stills, you will recognize
"layers".
With mulitiple tracks in video-editing, you create
"overlays".
The higher number of track (1,2,3,
4) takes presidence. It's possible to edit clips in
"high-numbered" tracks for instance by "Modify"-button. You can change size, motion, speed....
Just play around and see what happens,
and when you want something spesific to take place, you come
back and ask again.
Merry Christmas.
Just something.
https://www.petitpoisvideo.com