3.3 Rating and Ranking. What do I make of that?

Though rating and ranking sound very similar, they describe different concepts.

Rating: This is the estimated strength of a player.

Ranking: This is the order number of the player within the sequence of the active players sorted by their ratings.

Think of a high-jumper. His rating will be the hight that he got over. This is a physical measure. You cannot tell, whether it is an excellent job or a poor show unless you know the share of the players performing better or worse than the sportsman. And that's, when ranking steps in. But ranking makes only sense for active players (See section 3.5 How Can I Get a Ranking?.). After the high-jumper has retired (or even died) there is no point of assigning a ranking for him. But his rating remains valid forever.