Google acquired Jotspot in 2006 and then let it disappear. But the company didn't totally give up on the hosted wiki application and has rebranded it Google Sites. As Dan Farber notes, Google Sites is another cog in that Google Apps suite. Rafe Needleman finds it curious that Google Sites doesn't mention the word wiki anywhere.
That observation is keen. Perhaps wiki is too geeky. Perhaps Google thought a name like Google Sites was better than Jotspot. Frankly, none of this rebranding works all that well. It's still not clear what Google Sites is about judging from its name. Google is trying to mainstream the use of the wiki but without the name. But Google Sites doesn't exactly bonk you over the head with meaning either.
Overall, Google Sites is a collaboration app for people that are managing projects or classroom activities. In other words, it's wiki-ish.
More details are on Google's explainer. According to Google, Google Sites could power your intranet. More likely, however, is using Google Sites for education purposes. As for the branding--Jotspot to it's-not-a-wiki to Google Sites--Google didn't exactly clarify much of anything.
Also, Dennis Howlett: Google Sites - spoiled by usability issues