The hane White must answer
A sente endgame move is one the opponent cannot ignore — usually because ignoring loses stones. Right edge: White's two stones have exactly two liberties. Your hane at their head reduces them to one: if White plays elsewhere, the follow-up removes both stones outright. So White must connect — and you move first somewhere else. That is the whole trick of the endgame: bank every forced move first, then spend your real move on the biggest gote point.