SharePoint anonymous access permission

Came across a good explanation on what exact permissions that SharePoint anonymous access has:

"In SharePoint, anonymous users' rights are determined by the Limited Access permission level. Limited Access is a special permission level that cannot be assigned to a user or group directly. The reason it exists is because if you have a library or subsite that has broken permissions inheritance, and you give a user/group access to only that library/subsite, in order to view its contents, the user/group must have some access to the root web. Otherwise the user/group will be unable to browse the library/subsite, even though they have rights there, because there are things in the root web that are needed to render the site or library. Therefore, when you give a group permissions only to a subsite or library that is breaking permissions inheritance, SharePoint will automatically give Limited Access to that group or user on the root web.

......If you want to see what rights Limited Access is composed of in your site, go to http://SERVER/_layouts/role.aspx and click on Limited Access. "

For more descriptions, see the original post
http://blogs.msdn.com/b/ecm/archive/2007/05/12/anonymous-users-forms-pages-and-the-lockdown-feature.aspx