There’s a hidden part of the Internet that is much larger than the parts of the web you use everyday.
When you're checking your email, shopping online, or Facebooking, you are using what is referred to as the “Surface Web” or “Visible Web”
The "Visible Web" consists of web pages that are indexed by normal search engines, like Google or Yahoo. According to one estimate, there are at least 4 billion indexed web pages.
While this seems huge, there is a much larger part of the web that lurks below the "Surface Web" that isn’t indexed.
This part of the web is called the “Deep Web.”

The Deep Web

Here's the easiest way to think about the "Deep Web": It's all the data behind firewalls. Think user databases, business intranets, web archives, password protected websites, etc.
By some estimates, this part of the internet is estimated to be 400 to 500 times larger than the Surface Web.
Sometimes you will hear the terms Dark Web and Deep Web used interchangeably, but they aren’t really the same thing.

Cadie Thompson tells Codebreaker's Ben Johnson how common it is to buy drugs online:
 The Dark Web: Is it evil? Listen to the whole episode

The Dark Web

The Dark Web actually refers to a set of accessible, albeit anonymously-hosted websites that exist within the Deep Web.
Because these websites are not indexed by normal search engines, you can only be access them with special software that disguises your IP address.
The most common software used to access the the Dark Web is The Onion Browser, referred to as TOR. 
The Dark Web is much smaller than the Deep Web, and it's made up of all different kinds of sites. But it's perhaps most popular for its anonymous marketplaces that often sell illegal products like drugs or weapons.

Darknet Markets

Silk Road was really the first successful anonymous marketplace that thrived on the Dark Web.
Founded in 2011, Silk Road adopted an Amazon-like platform for vendors to buy and sell goods with the use of Bitcoin, an untraceable digital currency. The Silk Road's consumer-friendly approach and its guaranteed anonymity helped it quickly become the go-to website for contraband. 
By the time it was shut down in 2013, the marketplace had accumulated 1,400 vendors, 957,079 registered users, and had brokered more than 1.2 million transactions worth $214 million, according to the FBI.
Since Silk Road’s demise, numerous illicit marketplaces like Agora, AlphaBay, and others, have taken its place and business is actually growing. 
alphabay categoriesAlphaBay/screenshot
In fact, according to a study by researchers at Carnegie Mellon, the anonymous marketplace ecosystem does in excess of $500,000 a day.
What are people buying and selling? And how have things changed since Silk Road?
Listen to the latest episode of Codebreaker to learn more about how these sites operate and what people are buying. Or subscribe on iTunes or wherever you get your podcasts.