Keep An Eye ON & Keep An Eye OUT FOR 👀

Can you keep an eye on my son for an hour while I go out shopping?

Keep an eye on usually means take care of something or someone.

It can also mean watch, in certain contexts. I’m keeping an eye on interest rates, because I want to buy a house.

Keep an eye ON + NOUN

To keep an eye out (for something) means pay attention so you will notice it when you see it.

If I ask you to count how many red cars in a video, you will keep an eye out for red cars. You’ll pay attention and notice when you see them.

Keep an eye OUT FOR + NOUN.

Or just

Keep an eye out (when the context is clear)

A: Do you know any local English teachers?
B: No, sorry, but I’ll keep an eye out and let you know if I meet any!