Obtained this info today, placing here for reference :)

These are the definitions used by the WSS and FP client in summary usage reports (which are stored in the web metainfo):

  1. visit: a “total hit” that does not come from within the same server; that is, it either has no Referer header, or it has a Referer header from another server
  2. total hit: any hit that gets logged in the WSS http logs (we don’t log hits that result in error http results, or hits to the _layouts directory)
  3. hit: anything in #2 except hits on files with these extensions: "gif","jpg","png","bmp","css","mid","wav","ico","xml","au","js","class"

 

The detailed reports (which are stored in blobs in the webs table) tracks total hits.