Understanding the x-ray tactical motif? Can someone explain the x-ray tactical motif?  I have looked at this example, but I still don't understand it fully.  If you can provide other examples, that would be great too.
Basically, if a defending piece of your opponent has one of your pieces with the same movement "behind" it, then it's not really defending anything, as your piece standing behind also "attacks" what you want to capture through that defending piece of your opponent's.

In the following exampe, the ♞g6 is x-ray-attacked by the ♖b6, through the ♜d6, so once the other rook takes it, it is defended through the black rook by the ♖b6 (and the knight is lost).

[FEN "7k/4p3/1R1r2n1/P7/6R1/8/8/7K w - - 1 1"]

1. Rxg6