When trading bitcoin on exchanges you trade directly at the exchange (not through a broker). Another big difference is that everything at an exchange is visible publicly, this includes the current orderbook and a recent set of historical trades.

What is features are supported and what the fees are depend on the exchange, a few big exchanges are:

• bitstamp: They only support trading assets that you own, you can make limit orders or market orders. Margin trading is not supported.
• bitfinex: They support the same as bitstamp as well as margin orders.
• kraken: Similar as bitstamp, but also supports other cryptocurrencies.

Besides the top few, there are also exchanges that do not have markets with FIAT money, the biggest one here is poloniex (which supports margin trading).