Brawker is a decentralized platform that allows users to buy and sell bitcoins and use them to purchase products online. It aims to create an exchange for bitcoins that does not require a bank by generating the necessary keys and transactions for users in an encrypted and secure manner directly in their browser. The platform connects buyers and sellers of bitcoins so that John can use bitcoins to buy a headphone that Lucy offers to sell through bidding on the Brawker site.