Intraday trading means opening and closing a position, or buying and selling (or short-selling and covering) a security within the same trading day.
Intraday traders are active during market hours, buying, selling, shorting, and so forth, to capitalize on the movements of the markets during the day, and they primarily trade positions which are opened and closed during the same day. Intraday traders use technical indicators to find inefficiencies or price fluctuations that they believe will correct.
Many traders use algorithms to allow a computer do the trading automatically. These traders are also known as day traders and they may engage in this activity from their homes, anywhere in the world.