When a trader opens a position at AvaTrade, he is not charged any other commissions beside the spread. The spread is the difference between the buy and sell price which is counted in pips – the fourth digit after the dot. For example if the buy price of EURUSD is 1.1123 and the sell price is 1.1120, then the spread is 3 pips. The spread charged for a position opened by a trader is the spread multiplied by the size of the position.
The need to exchange currencies is the primary reason why the forex market is the largest, most liquid financial market in the world. It dwarfs other markets in size, even the stock market, with an average traded value of around U.S. $2,000 billion per day. (The total volume changes all the time, but as of August 2012, the Bank for International Settlements (BIS) reported that the forex market traded in excess of U.S. $4.9 trillion per day.)