Using a mixer might be a good solution to avoid be connected into the dark marketplaces, but why to use it bitcoin already does proctect those people under their adress wallet.
You must use a bitcoin mixing service if purchasing goods off the darkweb because bitcoin is easily traceable via the public blockchain, any coins you spend can be traced all the way back to where you purchased those coins from, if you used a service such as Coinbase to purchase your coins then you would had to have given them your personal detail at some stage and that's how they will get you.
All Bitcoin mixing
services can not be assumed to be legit in hiding your identity if you are going through the dark web. Remember, (*puts on tinfoil hat*) those services are there
for profit and all three letter agencies have to do is throw a little money their way in order to see who's mixing what, and so on. The best mixing service out there that I've seen would be CoinJoin, but even that has flaws since three letter agencies can easily just mix with your transactions by having enough inputs in there that can tell which one is yours.
I hope I could help you, don't hesitate to use google!
duckduckgo.
dark marketplaces can somebody explain me what is that in bitocin world i cant transalate that to understand
First, you would have to understand what Tor does and how it keeps your internet browsing anonymous. It can search clearnet sites (like the one you are on right now) and darknet sites, these sites usually have a long string of letters and number followed by .onion. So imagine Ebay, you can browse Ebay for things you want to purchase on the clearnet; but for other things that you can't find that people want to purchase (usually illegal things) they will go to websites that are hosted as a .onion site.
So it's not really related to Bitcoin directly... it's just used as a currency to transact between people pseudonymously