Space clearance If your bedroom is so untidy that you can/^t get to the cupboard to open it, then you have to clear a space in order to reach it. The same thing can happen in chess. A square or a diagonal may need to be cleared, either of your own or your opponent/^s pieces, so that you can play a winning move. If the White rook on g7 wasn/^t there, White could play Qg7 checkmate. So White played Rh7+ and if either Nxh7 or Kxh7, then Qg7++.
1.Rh7+
Nxh7
2.Qg7#
Try and imagine the position without the obstructing piece in the way. Look for a way of removing the obstructing piece without loss of time. In other words, create a threat, such as checkmate, or make a forcing move, i.e. check. 1-0