Silk Road is an online marketplace which launched in February 2011 and is designed to be completely anonymous. Just about every drug in existence is available on Silk Road, including Heroin, Cocaine, Methamphetamine, pharmaceuticals, and Cannabis. The only way to access Silk Road is through Tor, which is a browser that makes it nearly impossible to trace IP addresses. Bitcoin is the sole payment method used on Silk Road, since with Bitcoin you can send money worldwide near instantly and anonymously. Compare this to credit cards or almost any other payment method, where your personal information is needed to complete a transaction. Also Bitcoin payments can't be reversed, unlike credit cards.