For example, an investor who owns 500 shares of a certain stock is said to have an open position in that stock. When the investor sells those 500 shares, the position will be closed.
Buy-and-hold investors generally have one or more open positions at any given time. Short-term traders may execute "round-trip" trades; a position is opened and closed within a relatively short period of time. Day traders and scalpers may even open and close a position within a few seconds, trying the catch very small, but frequent, price movements throughout the day.
Investment dictionary. Academic. 2012.