The Dark Web is an encrypted section of the internet which can only be accessed using specific software.
There are other encrypted networks in operation, but the most famous is Tor, which stands for The Onion Router. The technology was developed by US military researchers to allow information to be exchanged anonymously by intelligence services.
Tor users by connect through a series of virtual tunnels rather than making a direct connection to the intended site. This means share information over public networks without compromising their privacy.
The Tor browser can be used to anonymously access normal websites, but sites that are hosted within the Tor network constitute the Dark Web.
It is known for being used for criminal activity, including the sale of weapons and drugs. For example, the dark net website Silk Road was an anonymous black market best known as a platform for selling illegal drugs.