If this helps people understand: The normal internet is like sending a letter from Blackpool to London through the post. You write your letter, write the address, and it's sent to London.
On TOR you write a letter from Blackpool, and send it to Manchester, with instructions for them to send it to Liverpool, who have instructions to send it to Essex, who have instructions to send it to somewhere else, on and on until the last stage where it gets sent to London.
With the normal internet it's easy to find who sent the letter as you just look at the return address. With TOR the return address is just the previous node, or "city". Tracing means tracing back every single stage, it's not impossible but it's much harder to do.
This means that criminals use websites like this as the chances of them being found are much lower. The dark web itself is just a tool to keep your internet use private by hiding where it comes from. There are legitimate uses for this - think countries where being a whistle blower would get you killed, or a journalist talking to a source.
It is used for bad, but it wasn't made to be used for bad. There is normal stuff on there and you are not automatically a bad person for using it.