A community site is a scaled down social network. There is no chat facility or access to the main administration area.
Comments can be made by members on a page. Please consult the Comments area of the help guide for more information.
The main difference to a normal site would be the addition of a news activity feed whereby members can easily get a view on all the updates to the site plus post their own contributions to various areas on the site simply on one page.
Each member has access to their own profile as in the comments area.