How to apply the ko rule (Go)
Ko only prevents a player from making a move that would have the effect of returning the board to the position that it was in just before his opponent's last move only. So the only thing you ever need to keep track of is what the board was like just before your opponent made his last move; you cannot move such that it would recreate that position.

All the further description in the wiki is explaining what a player will do if the move they want to make it prevented by ko. They make a move somewhere else on the board that forces black to respond to it; thus freeing them to make the play that they couldn't have played the previous turn due to ko.