I am really confused about the terms called communities,Site.com sites,Site.com studio,Force.com sites and community builder.If some one could please tell me what it's mean.When to site.com studio ? Site.com is same as Community Builder.
Here's how they seem to be defined as of March 2017:
Communities - Sub-domain sites built with Community Builder (Lightning), standard Salesforce UI (Tabs), or custom Visualforce.
Community Builder - A UI for click-and-drag construction of community pages.
Site.com Studio - Replaced by Community Builder (except for a couple features that take you back to Site.com Studio).
Site.com Sites - Replaced by Communities built with Community Builder.
Force.com Sites - Sub-domain sites that have no authentication built with Visualforce. (Authenticated VF communities are built in much the same way, but are technically distinct because of authentication).