http://whirtorrocbwdo7sgkww2q2uxajxlg33uzzpbtbqwik2natfinbmtaad.onion/blog/bitcoin-mixer
For example, imagine that Alice wants to send 1 Bitcoin to Bob. If Alice sends the Bitcoin directly from her wallet to Bob's wallet, the transaction will be recorded on the blockchain, which is a public ledger of all Bitcoin transactions. Anyone can see that Alice sent 1 Bitcoin to Bob, and they can also see the transaction history of both Alice's and Bob's Bitcoin addresses.