One of the important factors to take into account is 'control' of squares, ranks, files and diagonals. But what exactly, does it mean when we say that a player 'controls' space?
The reason I ask is that many, many times, I have seen commentators say 'white plays Re1 to control the open e-file'. I was looking at a game some time ago, and sure enough, this comment was made. But when I looked at the postion, the only other square that the rook could occupy WITHOUT BEING CAPTURED was e2. It couldn't occupy any other square along that file, all of which were covered by black. So, how can you say that the rook was 'controlling' the e-file?