ELI5: What is the dark web and how do .onion websites work?

The dark web is a hidden part of the internet that you cannot find using normal search engines, and it can only be opened with a special browser that keeps your identity completely secret.

Think of the normal internet like a regular shopping mall with big, bright glass windows. When you visit a website like YouTube, the shopkeeper sees you walk in, and you can see their store sign from the street.

The dark web, however, is like an exclusive, members-only clubhouse hidden behind a secret door in an alleyway. You cannot see it from the street, Google cannot map it, and you need a special pair of "disguise glasses" called the Tor browser to find and enter it.

Websites in this hidden area end with .onion instead of .com. They are called "onion" sites because of how they protect your privacy, working just like the layers of a real onion:

• Layered envelopes: Imagine you want to send a secret letter to a friend. Instead of mailing it directly, you put it inside three envelopes. You hand it to the first mail carrier, who peels off the outer envelope to see where to send it next.
• Passing the package: The second mail carrier peels off another envelope, and the third peels off the last one before delivering it to your friend.
• Total secrecy: None of the mail carriers know the whole journey. The first one only knows who sent it, the middle one only passes it along, and the last one only knows who receives it. Nobody knows both who you are and what website you are visiting.

In everyday life, people use this hidden part of the internet for different reasons. Some people use it for bad things because they think the police cannot catch them. However, many good people use it too, such as journalists sharing important secrets safely, or people living in countries where the government blocks regular websites and spies on regular citizens.