Probably they are just kind of wallet that has anonymity transactions. Just like the Wasabi wallet it can generate a temporary wallet and mix your coin with Coinjoin. But probably I dont think how many times it will tumble into different addresses per transaction.

I voted Chipmixer because I never heard about the serious complaints against them or something fraudulent issues.

Here is also a thread of Bitcoin mixing website list, 2020 List Bitcoin Mixers Bitcoin Tumblers Websites, just for in case if you want a reference.