It's just the name of the resort. VWL (Villas at the Wilderness Lodge) also has "villas" in its name. The accomodations at all of the DVC resorts are quite similar, but there are some differences. For example, rooms at OKW are larger than those at BWV, VWL & BCV. Only OKW & BWV have "Grand Villas" (3 bedroom units).
I am not as familar with the rooms at VB & HHI so if you have specific questions about those, ask away. There are lots of posters who know about those two resorts.
The Boardwalk resort has two sections -- The Boardwalk Inn and the Boardwalk Villas. The Inn is a Disney Deluxe resort and not part of the DVC. The Boardwalk Villas is the section that is owned by DVC members (but is available for booking through Disney as well).
The "Villas" are for the special "gold" members. It's a secret society for the very very obsessed. I'm a member, of course, but I'm not allowed to tell you anymore about it.