Silk Road
Silk Road was shut down by the FBI and its owner was arrested on Oct. 1. Twitter/OliverSmithEU

Silk Road, the infamous black market hidden in the Deep Web, was seized and closed by the FBI on Wednesday. According to a leaked complaint, the FBI has arrested the owner of Silk Road -- Ross William Ulbricht, known online as “Dread Pirate Roberts” -- and charged him with narcotics trafficking conspiracy, computer hacking conspiracy and money laundering conspiracy.

The seizure of Silk Road raises questions about how secure the Tor network, an anonymous Web-browsing system that is required to access Silk Road, actually is, as well as how the government will go about prosecuting such an unstructured, anonymous and international organization.

But the question for most people is, what is Silk Road? The vast majority of users can’t even access the website to see what it's about. So, how does a website stay underground, and why did the FBI shut this one down?

Here are four things you need to know about the now-defunct Silk Road marketplace.

1. Silk Road Was On The Deep Web

In cyberculture, the vast majority of the public uses websites from the Surface Web, which is content indexed by standard search engines. If you can Google it, it’s on the Surface Web.

The Deep Web is content hidden from these indexes, meaning search engines cannot find them and retrieve their content. This makes them pretty much nonexistent to most people. The Deep Web was home to all kinds of stuff, but a group of sites used the .onion suffix, meaning they could be accessed only via Tor, a software for enabling online anonymity. Silk Road was a part of this group, with the Web address “silkroadvb5piz3r.onion,” and it used this to remain underground.

2. 70 Percent Of Silk Road Was Drugs

Silk Road is most famous for selling drugs that are illegal in most countries. An estimated 70 percent of merchandise available on Silk Road was drugs, including heroin, LSD, cocaine, MDMA and marijuana. It is known by some as the “ of illegal drugs.”

The site had a policing feature to prohibit any product that had a purpose of harming or defrauding -- child pornography, stolen credit cards and weapons of mass destruction, for example. However, the recent FBI charges claim that Silk Road offered tutorials for hacking ATM machines, contacts for hit men and counterfeiters, and guns.

Among the legal goods sold on Silk Road were art, clothes, books, cigarettes and jewelry, as well as legal services.

3. Purchases Were Made With Bitcoin

Ah, yes, bitcoin, that digital currency that has grown so much in value and public awareness in recent months. Bitcoin is based on an open-source cryptographic protocol that allows transfers between users without a central authority. This helps bitcoin transactions remain almost as anonymous as cash.

Credit cards are, of course, anything but anonymous, so Silk Road allowed purchases only with bitcoins. While bitcoins aren’t completely untraceable, they do make it much more difficult to figure out who is buying or selling narcotics through Silk Road.

It’s estimated that $15 million worth of transactions are made in bitcoin annually on Silk Road.

4. Ross William Ulbricht Is “Dread Pirate Roberts,” The Silk Road Owner

The criminal complaint identified Ulbrich as the owner of Silk Road and publishes some very detailed information about him. The FBI said it used LinkedIn to identify Ulbricht as a 29-year-old who graduated from the University of Texas in 2006 with a bachelor of science degree in physics. Ulbricht also studied at the University of Pennsylvania School of Materials Science and Engineering from 2006 to 2010.

The complaint details how the FBI identified and located Ulbricht, who was living in San Francisco. He was in possession of 26,000 bitcoins, equal to about $3.6 million.