ask the spam accounts. i'm sure they'll be happy to fill you in... [it's serving static - pre-rendered html - web pages. like blogging with github or bitbucket, for example.]
[at time of posting half of comments were new accounts with content-less "wow" comments. [or people who don't know how to edit posts. haha.] if that's cynical i'm a pink giraffe.]
Basically, instead of hosting a database on your server and using php to generate the pages on every request, like Wordpress does, you just create a text file for every page, and precompile your entire site into raw html files, so that it's really fast because there is no processing on the server.