Grandmaster Alexandra Kosteniuk, in this chess video tutorial, you guessed it, teaches you how to play a game of chess.
This chess problem is from the game Fressinet vs Kosteniuk, in Villandry (2007). It's Black to play and win. In a game of chess, when it comes down to just a Black King and Pawn, and a White King, you think it might be little time before Black wins the chess game, but if you miss it, it just might mean a million more moves, or at least a hundred.
Alexandra missed the continuation needed to win and had to play 167 more moves to win the chess game. Knowing endgames makes you a stronger player, and you can go home earlier because of it.