The purchase and sale of a security within a short period of time, usually on the same day.
Investopedia Says:
Generally speaking, this is the strategy of day traders, where they attempt to profit by buying or short selling large quantities of stock to capitalize on small changes in price.
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Active trading is an investing style that aims to beat the market. Find out how it works, and whether it will work for you. How To Outperform The Market
Learn about this controversial way of investing. Day Trading: An Introduction