Triangulation in Chess
Triangulation is one of the most elegant endgame techniques: the king makes three moves to end up where it started, but now it's the opponent's turn to move. This transfers the opposition and can turn a drawn position into a win.
How triangulation works
The king occupies three squares in a triangle (e.g., d3-e3-d4) while the opponent's king can only move between two squares. After three moves, the position is identical, but the move has been transferred. Now the opponent is in zugzwang and must make a concession.
When to use it
Triangulation is most common in K+P endgames when direct opposition doesn't work. If the opponent can maintain opposition by copying your moves, you need a triangle, three squares vs their two, to outmanoeuvre them.