You can take it as a bridge which connects two different interfaces! Of course, the concept of bridge doesn't just connect two different interfaces, e.g. PCI bridge.
A wrapper is sometimes just to refer to one smaller block used to connect the current inferface to the new interface so that these two different interfaces can be commnunicated now! This ofter happens when you buy a off-the-shelf IP that is not compatible with your current bus! For example, one Wishbone interface and one AHB interface!
When the Wrapper is rather robust/functional/configurable, now it can be conceived of it as a Birdge, more suitble!
Maybe helpful!
Thomson