It appears to insert https:// into the urlbar of the current address without any effect on page content. Although manually hitting Enter will submit the HTTPS request, I recommend https://addons.mozilla.org/firefox/addon/httptohttps/ instead, which toggles between HTTP and HTTPS and reloads the page automatically with a toolbar button.
Only adds an "S" to http. It does NOT encrypt, it is not secure. No SSL Validation