Trading is the process of buying and selling securities in the stock market with the intention of making a short-term profit. Some traders, known as day traders, only hold stocks until the close of the market at the end of each day; others, known as active traders, may hold stocks for weeks. In either case, trading is distinct from investing, which also involves the buying and selling of stocks and bonds but with the intention of making long-term gains over years or decades.
Trading plays an important function in improving the efficiency of markets, as traders seek out arbitrage opportunities to profit when pricing of a security strays too far from its fair market value. Today, with high-volume, high-speed algorithmic trading by computers making up a majority of activity on the market, some critics have questioned whether so much short-term trading is exacerbating volatility.
While debate continues, it is clear that this type of financial engineering approach to trading is here to stay, and will continue to push the evolution of this field as it progresses beyond its roots on the floor of the stock exchange.