High-Frequency Trading (HFT): Also known as algo or algorithmic trading, HFT is computerized trading at high volumes and speed using powerful computers and complex algorithms, often of a proprietary nature. HFT can be split into two types: execution and opportunistic. Execution trading is used to find the best possible price for an order and may involve splitting the order into smaller pieces and executing at different times. Opportunistic trading uses algorithms to find small trading opportunities in the market based on conditions rather than completing a specific trade.

Sources: Investopedia, NASDAQ.com