Binance Coin (BNB) is an Ethereum-based ERC-20 token. The token is designed to be used on binance's trading platform. On the platform you have the option to pay the trading fees with BNB at a discounted rate. Binance has announced that they will develop their own blockchain in the future. BNB was one of the best performing cryptocurrencies of 2017. They also plan to create a decentralized exchange for blockchain assets.