User Manual vs User Guide vs Documentation vs Quick Reference vs Handbook

I am aware this has already been asked at http://english.stackexchange.com/questions/59224/what-are-the-differences-between-manual-guide-and-instruction however from a user experience point of view, what is the most straightforward name which we could use for the section which will contain our software documentation in our website and in our software under the help section?

So far we made a mess of different naming conventions for the same thing and went as far as making smaller subguides called "pills of". Of course this made a huge confusion so we wanted to make a final naming convention for all our products.

Moreover, should these documents/manuals or whatever we will call them, be filed under "support" or "documentation" or is there some more obvious way to group all the documents of different softwares?

Any suggestions?