People mostly use the deep web for illegal activities because the whole point of it is that it is extremely difficult to trace the user because IP addresses are not passed on, and the traffic is routed through many different servers in differet countries. The most prolific uses are for illegal porn, file sharing and virus related activities aswell as terrorism and other things, this is why governments are closing in on this system and working on stopping it. Most people who use the Tor browser know a lot about it before they use it, they know how to properly configure the browser and so on, novices can get ther fingers burnt very quickly either by being discovered when they thought they were hidden. So, if you are going down that route learn as much about it as possible first rather than finding out the hard way. I didn’t, I tried it and realised I was not capable of safely using it or even understanding it all so I never used it again. It may have cost me several hundred pounds aswell, I can’t prove it but let’s just say something rather unfortunate happened after I installed Tor, it could have just been coincindence, I’ll never know.