Web browsers often send the url of the last page visited in the REFERER variable of the HTTP Header. This information is useful as it helps webmasters discover the source of their web traffic.
This variable is just a freeform field. Browsers can put anything into the variable. Spammers often fill the field with garbage.
This first report shows referrers associated with your IP address (if any). The second report shows referrers to this site.