Bitcoin Mixer is a Tor Hidden Service that allows you to mix bitcoins with other users to make the bitcoins anonymous. To access the Bitcoin Mixer site you must use Tor.
As bitcoin is not anonymous without a bitcoin mixing service, anyone can see the flow of bitcoins from address to address on the public block chain. To break this chain you need to use a bitcoin mixer or also called a bitcoin laundry. Bitcoin Mixer is a bitcoin mixing service set up to help people stay anonymous, it’s used to mix your bitcoins with other users to break the track to the bitcoins original source. Bitcoin Mixer will receive your bitcoins on one wallet and then send bitcoins from another wallet to a address you specify.