It is said as a way to give a warning or notice of something to come. example: Heads up, I will not be able to come to your party on Saturday. I hope this was helpful!

Yes to what the others said. Also, if someone shouts "HEADS UP," it literally means WATCH OUT - something might hit you. For example, if you were working on a roof and you dropped your hammer you might yell HEADS UP to warn the people below.

Heads up means a warning that something is going to happen, so that you can prepare for it.

“ Be aware “

Yes.