When looking at the history of a page, if one sees this at the top...

This is an old revision of this page, as edited by Bozo the Clown(Talk) at 12:00, 25 December 2008. It may differ significantly from the current revision.

What this means is that the version one is looking at is the most recent version and that the person named is the one who made the most recent edit.

In order to see what that edit was, it is necessary to look at the actual edit. So for instance, Crusty the Clown might have made an edit to a page (lets say the Circus Clown page), in which Crusty accuses Bozo of having an affair with Beppo the Clown, and also saying that Chuckles the Clown put itch powder in Beppo's face cream. Bozo might see that and decide that he wants to remove the reference pertaining to himself, but leave in the reference to Chuckles (because Bozo knows that Chuckles can remove that reference himself).

What happens then, is that anyone who looks at the history will see that the most recent change was made by Bozo, and they will see the reference made by Crusty about Chuckles. It might be easy to conclude that Bozo was the one who added the bit about Chuckles, but that would be an incorrect conclusion.