The Dark Web is classified as a small portion of the Deep Web that has been intentionally hidden and is inaccessible through standard web browsers. The most famous content that resides on the Dark Web is found in the TOR network.
Transactions on the dark web are often made in cryptocurrencies, previously Bitcoin, but more recently privacy coins such as Monero or Zcash are more commonly used.
The primary attraction of the dark web is the ability to maintain anonymity when buying and selling goods and services. While many of the transactions are illegal in nature, some uses of the dark web are more noble, such as a journalist who might use the dark web to conduct interviews with citizens in repressive regimes.
Estimates have been made that dark web sales were between $150-180 million in 2015, but the very nature of the dark web makes such estimates nearly impossible, and there are some who have said dark web commerce could reach $1 billion by 2020.
In addition, it has been nearly impossible for law enforcement to handle illegal marketplaces on the dark web, because the OpenBazaar software allows new decentralized sites to spring up overnight.