See usually means noticing something with your eyes.
- I can see the mountain.
- Did you see that car?
Look means directing your eyes towards something.
- Look at this picture.
- Look over there.
Watch means looking at something for a period of time, especially something moving or changing.
- We watched a film.
- She watched the football match.
- He watched the children playing.
Simple guide
See = notice.
Look = direct your eyes.
Watch = look for a period of time.