What are long (buy) and short (sell) positions?
A long position, or buy order, is made when an investor expects the price to rise. It is opened at the ask price and closed at the bid price. You make a profit when the bid price is higher than your opening price.
A short position, or sell order, is used when an investor expects the price to fall. It is opened at the bid price and closed at the ask price. You profit when the ask price is lower than your opening price.