First of all, I would advise you to get hold (through ftp) of your log files, as they possibly contain a lot more information than your host is providing you. There are some decent analysers available to work through the logfiles and provide you with statisitics. (see also some of the recent threads in the webdevelopment forum).
OK about your question:
- a hit is any time your server is requested for information. This could be (and often is) some unrelated webpage requesting an image that resides on your site, but also all the information that your visitors request.
- a visit is someone actually requesting one of your pages and usually there will be one visit per visitor session. This means that if I were to enter your site, I get recorded as a visitor, and as long as I am active, that only counts for one visit. However, if I go away for lunch and come back to continue surfing, my previous session has ended as far as your server is concerned, and so I will start a new session and be logged as a new visit.
-I don't know about entry and exit counts, but I do know about entry and exit pages.
See also this very helpful page:
http://www.plugsocket.com/support/site_statistics.html