Instructive K+P endgame
This is a game I played against my friend Joseph. Ratings aside, Joseph is a much better player than me, and in this game, outplayed me most of the way. But I had a saving grace in the ending.
White is on the move in this diagram. A tempo ahead. He will queen his pawn first. And queen it on the diagonal of my own queening square! Yikes!! How then do I save the draw?
The key here is that in an endgame, with a King + Queen against a King + Pawn, the side with the Pawn can draw, if the pawn is a rook pawn or a bishop pawn, and if s/he can keep the opposition Queen off the queening square for her/his Pawn, and the pawn can reach the seventh rank.
Any other pawn loses, and the principle of the draw is being stalemated (or queening). Unless the White King, in this case, is right in the action, White can not gain the tempos to deliver mate.
This instructive endgame is explained in Reuben Fine's "Basic Chess Endings."