Another type of centralized exchange is meant primarily for trading cryptocurrencies. Bittrex and Poloniex are good examples of this type of exchange, which typically allows for the exchange of dozens, if not hundreds of different cryptocurrencies.
A third type of exchange is the decentralized exchange, where the exchange doesn’t hold customer funds, but only acts as a matchmaker between buyers and sellers. 0x is one such example that uses an order book to provide decentralized trades. Kyber Network is another which provides complete trustless decentralized trades right on the blockchain.