Refers to computerized trading using proprietary algorithms. There are two types high frequency trading. Execution trading is when an order (often a large order) is executed via a computerized algorithm. The program is designed to get the best possible price. It may split the order into smaller pieces and execute at different times. The second type of high frequency trading is not executing a set order but looking for small trading opportunities in the market. It is estimated that 50 percent of stock trading volume in the U.S. is currently being driven by computer-backed high frequency trading. Also known as algo or algortihmic trading.