The interview is in two parts, the first, below, largely deals with Wikipedia, and the Second Part Of The Interview deals primarily with Wikia.com.
Wikipedia probably needs no introduction, but in case you've been living in a cave for the last decade, it is a free open sourced encyclopaedia which brings fairly reliable knowledge to the masses. It is a life long passion for founder, Jimmy Wales, and has been a runaway success, being one of the most respected sources in the Internet, and ranking about number 5 of all web sites in popularity.
The open user contributed nature of it, has occasionally been the butt of jokes about it's reliability, but the fact is that it is heavily moderated by a team of volunteers, and most articles cite their sources.
Wikia.com is a commercial appliance of the technology behind Wikipedia, where anyone can create a wiki on any subject of their choice. It is typically used for fictional material like Video Games, Movie universes, and TV programs, although they are keen to encourage other areas like sports.
Personally, I find the second one fascinating as an aspiring entrepreneur myself, I'm always looking to find commercial Internet models that work, and Wikia.com has proved to be a runaway success, providing a rich eco system for fans, as well as a sound commercial model. The production team of Lost, even started relying on the Lost Wikia when writing scripts!