Here’s a nice vintage video by Hamilton, explaining the basics of how a mechanical watch works.
Very informative (for most of us) to see. And the fact that it’s a vintage film it ironically indicates that not much has happened in the way mechanical time pieces are constructed to indicate time.
As an addition, an automatic winding watch has exactly the same construction as the here shown hand winding movement. It just has an extra construction (with a weight rotor, mostly positioned below the movement) which winds the crown by moving the watch (and thus turning the rotor) in stead of winding it by hand.