The buy side of an order is a position held when the investor expects the price to go up, otherwise known as a “long position”. It is opened at the “ask price” and closed at the “bid price”. When the ask price is higher than the opening position price, you’ll make a profit.
The sell side of an order is a position held when the investor expects the price to drop, otherwise known as a “short position”. It is opened at the “bid price” and closed at the “ask price”. When the bid price is lower than the opening position price, you’ll make a profit.