The dark side - it sounds so evil. Darth Vader and "The Force" used for the wrong things. Online there are a number of "dark" places: darknet, dark web, black web, and black net. And then there is the deep web, which is often associated with (and confused with) these other dark places.
The deep web is all of the information stored online that is not indexed by search engines. You probably use Google for search, but it only indexes a fraction of the Internet. Some estimates say that the web contains 500 times more content than what Google returns in search results.
The results you get when you do a search on Google and other search engines dome from the “surface web.” The results that you're not getting returned would be from the “deep web” or “invisible web”.
Are those things hidden because they are evil or illegal. Actually, much of it hidden for less dramatic reason. Some of it probably would not be relevant to most searchers, or it's old and outdated. A lot of it is in databases that Google is either not interested in indexing or barred from accessing. That is sometimes good for our privacy. You wouldn't want Google to be indexing your phone apps, the files in your Dropbox account, or your social media accounts. Other places, like subscription academic journals and court records are also deeper in the web than search engine can or want to go.
Actually, Google has a separate search engine called deeperweb.com. Give it a try. Search for yourself or some "deep" subject. It doesn't really go deep into the dark and scary Net. Reading their tutorial, you find that DeeperWeb is their metasearch engine that employs tag cloud techniques for navigating through regular Google search results and using Topic Map methods gives results relevant to a specific topic.
A lot of social media shares occur in what some people call “dark social” which comes from the “dark web” but it might be better called "deep social."
The dark web is different from the deep web. This darker side is is only accessible by means of special software. Many people using that software to search want to remain anonymous or untraceable. That does sound a bit evil - and it might be. Although someone might be searching anonymously because they would be embarrassed by their search being discovered, someone else could be trying to avoid law enforcement. These darknets form a small part of the larger deep web.
Dark web sites are also where narcotics, firearms, and stolen credit card numbers are bought and sold. They are sites that get shut down sometimes because someone uses them to search for hitmen or share pornography or something else illegal.
But it is not all evil. Journalists and whistleblowers use it to exchange sensitive information. Depending on how you view someone like Edward Snowden, this usage is either treasonous or heroic.
The most common way to access this darknet network made up of servers scattered around the world is through something like Tor. The name is short for The Onion Router (Darknet website URLs often end with .onion rather than .com or .org.) The Tor browser relays traffic through encrypted connections and all the traffic bounces between relays located around the world, making the user "anonymous."
Before you decide to go over to the dark side, know that although your ISP and the government might not be able to view your activity when on the Tor Network, they do know you are on the Tor Network. As this guide to the deep and dark web notes, "that alone is enough to raise eyebrows. In fact, a recent judgment by the US Supreme Court denoted that simply using Tor was sufficient probable cause for the FBI to search and seize any computer around the world."
Many Tor users add a further layer of security via a Virtual Private Network (VPN). But I use VPN provided by my university in order to connect to the their network from off-campus using my own Internet Service Provider (ISP) and have secure access to the university's network resources from anywhere at anytime. Every tool can be used for good and evil.