The dark web is essentially a hidden network. Normally, the average person can't access it through means like searching; it usually requires specific software, network configurations, or designated authorized addresses to access.
The biggest characteristic of the dark web is its concealment, so a lot of illegal and criminal activities use the dark web to conduct transactions or provide information. This includes not only transactions of various illegal devices and weapons but also pornography, gambling, drugs, personal information, etc. It's basically a hodgepodge black market.
The dark web has always been an area of focus for surveillance by the FBI and other agencies. But the dark web is dark precisely because no one provides clues for addresses and access information, making it hard to find.
