In the opening and middle game, it is usually the number of moves a player has available behind a frontline. In the diagram below, the player to move loses the game. Of course this position is as artificial as it is double-edged, but the point is that there are many positions where tempo is more crucial than pace. Place all men two ranks up and white, if he were to move, would still lose, despite 24 tempi advantage in terms of pace. As far as anticipating the nature of the game goes, the decision whether to keep men back is a strategic one.
Games naturally start out closed.
There's no large body of games to illustrate strategy. Most of these are largely uninvestigated.