Size: it has a huge trading volume of about $5 trillion per day, making it the largest liquid market in the world.
Volatility: the volatility of the market in the area of fluctuating exchange rate, coupled with the huge trading volumes makes it highly competitive.
The use of leverage: traders can make use of leverage to enhance their profit and loss margins. For instance you can control a position of $200,000 by placing just $2000 upfront and then leverage the rest from your broker.
Global structure: It is a decentralized market, operates 24 hrs a day, 51/2 days a week with high liquidity throughout the period.