If the player whose turn it is has no legal moves the game has to end. If this player is not in check it is called stalemate. Stalemate ends the game and the result is a draw, even when one of the players has a big material advantage.
The following two diagrams are stalemates.



So you have to be very careful and avoid the stalemates especially when you are a Queen ahead. The next two diagrams do not represent stalemates.
Do you see why?



The black King has no legal moves, but black still has legal moves. He has to move his pawn. After the pawn move it is white’s turn. And both diagrams result in a mate in one problem.
Can you solve it?

For the first diagram there are four solutions and the fact that black’s pawn may have been promoted to a Queen (or another piece) doesn’t matter.

The next lesson tries to explain why chess lessons start at the end.