Could someone please explain the difference between a checkmate and a stalemate to me?

I honestly don't understand the difference, because sometimes I'm about to win a game, and then instead of saying checkmate, it says stalemate, and instead of me winning, it's a draw.

Checkmate is when the king is in check and has no legal moves to get out of check.

Stalemate is when the king is not in check and the player has no legal moves on the board.

In checkmate, the king is in check and can't escape.

In stalemate, the king isn't in check and the player has no legal moves.

Okay, thank you!

If the opponent is IN CHECK and has no legal move, it's checkmate (a win).

If the opponent is NOT IN CHECK and has no legal move, it's stalemate (a draw).

Checkmate: King is in check and can't move anywhere.

Stalemate: King is NOT IN CHECK but, can't move anywhere!

His other pieces can move if they can. Then it is not Stalemate 

Okay! Thank you all so much!

No problem!!!

Checkmate is when the king is IN check and in the next move, their king will be captured. A stalemate is when the king is NOT IN check and has no legal moves. This refers to the chess rule"you can never put your king in check"