In October 2013, the FBI shutdown Silk Road, a popular online black market where users could buy drugs, weapons, and even assassins. While this marketplace was operating on the Internet, you'd be hard-pressed to find it via Google. In fact, you would have to be part of a secret network that operates in a small portion of the Internet known as the Deep Web.
See also: Deep Web Film Will Go Inside the World of Bitcoin, Silk Road and Beyond
So what is the Deep Web exactly, and what seedy, nefarious activity happens there? Well, you might be surprised by the answer (hint: that private photo album dedicated to your cat is part of the Deep Web).
The newest video in our Mashable Explains series covers everything from search engine crawling to the Darknet — all in two minutes. After you watch the video above, subscribe to Mashable on YouTube for more.