TOR is an achronym for "The Onion Router" and is an anonymous web browser that allows you to access websites and data without being easily tracked (like most web browsers). Privacy is clearly one reason to use TOR, but using TOR also gives you access to parts of the web that aren't accessible otherwise, like Silk Road where you can buy all sort of things that are likely legal and illegal in your country, using bitcoins. So be careful, but there's a wonderful world out there. By the way after you are set up with TOR you can access Silk Road with this link (won't work with a normal browser) http://ianxz6zefk72ulzz.onion/index.php