What is a checkmate?

Can someone please explain to me and give an example?

A checkmate is when a king is attacked, and

• He has no safe square to move to
• The attacking piece cannot be captured
• He has no piece which can interpose and block the attack

Your opponents should regret resigning.

It is when your in check and you can not move out of check. That is checkmate. Your king is traped

I know you know what checkmate is... 
But I think you are asking why they call it checkmate?
In hockey, a check is a good knock to get them to topple over...and to mate, well, put them in a position where they can not move. I could be wrong, never really researched it, but it is what it is.

"shāh māt": "the king is helpless" or something similar

ur 1277 standard rating, so figure it out urself!