The mixer is the first application aiming to improve the anonymity and fungibility of IOTA. As mentioned in the above post, as with most cryptocurrencies, IOTA’s ledger is transparent by design. This means that all transactional data can be viewed on a website like the IOTA Tangle Explorer. While Masked Authentication Messaging may be used to encrypt messages sent over the Tangle, it cannot be used to exchange tokens.
Token mixing is useful here, because it can start to add a level of uncertainty in the ledger, breaking the links of ownership between transactions, which was previously impossible. Iotas that are sent into the IOTA mixer come out with no taint to the original payment address on the Tangle, and furthermore funds are divided up between multiple addresses at random intervals. The FAQ on the website contains details about how to use it, and how it works.
The mixer represents an example of a fast full-stack IOTA application, which amongst other features manages its own wallet and reattaches to the Tangle automatically. Developers interested in working with the IOTA network might be pleased to hear that there are plans to open source the codebase and associated documentation soon.