Where is ths Site Features documentation?

I'm trying to learn about site features in SharePoint 2013 and I've realized there pretty much is no documentation for them.

For example, searching for "SharePoint 2013 "Class Web Types"" (I don't know what this is...) for example, yields;

bing.com

4 hits, only relevant one is http://office.microsoft.com/en-us/sharepoint-server-help/activate-features-for-sites-HA102772224.aspx

google.com

1 hit (English only) pointing to same document http://office.microsoft.com/en-us/sharepoint-server-help/activate-features-for-sites-HA102772224.aspx

I'm afraid "Class Web Types - Adds required content types to the SharePoint class web" doesn't help me learn about this (what is "SharePoint class web"?).

Any ideas on how I can educate myself around this (and other) feature(s)?

Thanks!

Paul