i think that they create these websites same as normal ones, just main difference is that they sell illegal stuff there, but i am sure that there is tutorial for that
Dark marketplaces are very bad. There are indeed a lot of scammers and you can buy some illegal stuff and that is not good. But you cant stop people to not using that and that is the problem but try as much you can. you do that.
I still dont get it. What type of illegal stuff is sold in Dark Market places and how you can be sure that such stuff is not pasted on normal sale websites?
Dark Markets involves payment in bitcoins, so that are called darknet ? Can we buy legal things also from darknet as the prices are lesser

Yes, we can buy legal things there, but most of them are illegal things, actually I think the Customer will withhold those packages.