The forex market is traded over the counter through an electronic network of Banks, Broker Dealers and Hedge Funds. There is no centralized physical exchange like with equities or futures. There are some key advantages to this. One key advantage is that the Forex Market is open 24 hours a day 6 days per week. The hours are from Sunday starting at 5pm going to Friday at 5pm New York Time. The market begins in Australia (Sydney) and continues around the world to the United States (New York).
Because the network of banks, brokers and dealers is so large, liquidity becomes a smaller issue than if you were dealing with some stocks or futures. During normal market conditions getting in and out of trades is a fairly smooth process, with a counterparty or a market maker usually available to facilitate your trade.
Another benefit of forex trading is that since you are not taking positions in companies there is no uptick rule. Therefore you can take a particular currency pair and speculate on it going up or down without any restrictions.
Information and market news broadcasts are broadly available to all traders in the FX Market. Therefore, particularly through the use of technology, the market is fairly transparent to the investor.