See, Watch, or Look?

Watch: to look at something for a period of time, especially something that is moving. We watch something when we are interested in what happens.

• Could you watch my purse while I go to the restroom?
• I love sitting at the window and watching the people walk by.
• We watched the basketball game on TV.

See: 1 to be aware of what is around you by using your eyes,
2 to watch a film or TV program

• Did you see Desperate Housewives last night? It was a rerun.
  
• When you see Jenny, please tell her not to be late for the party.
• Do you see that white church? That's San Agustín.

Look: to direct your eyes in order to see

• Look! There's Marlene with her boyfriend.
• Look over there - do you see that red bus?

Look at: to view something, to be interested in the appearance of something

• Look at Martha, isn't she pretty today?
• Can I look at your answers? Mine are all wrong.

See is usually used for something stationary or static (not moving)
E.g. You see blood, see the stars, see a picture/photograph, see a painting

Watch is usually for something that moves, or that requires attention
E.g. watch a movie, watch children playing, sports

Look (at) is to pay attention to a detail, or appearance
E.g. You can look at people, objects

Note:
Look at the children! (Check out their appearance or what they are doing. Do not pay a lot of attention to them, though.)
Watch the children, please. (Pay attention to them so that they don't get hurt or in trouble)
I can't see the children. (They are not within my view.)