When an endgame with King + Rook + Pawn against King + Rook is a draw?
Philidor's position (I haven't learnt it myself yet), but I imagine there are other drawn scenarios.
Learning Philidor's Position and the Lucena position are on my to do list! ;)
Along with the Knight and Bishop Mate (for next year)
When an endgame with King + Rook + Pawn against King + Rook is a draw?