The buy side of an order is a position held when the investor expects the price to go up, known as a "Long Position".
It is opened at the"Ask Price" and closed at the"Bid Price".
When the market bid price is higher than the open price for a long position (Ask Price), you will make a profit.
The sell side of an order is a position held when the investor expects the price to go up, known as a "Short Position".
It is opened at the"Bid Price" and closed at the"Ask Price".
When the market ask price is higher than the open price for a short position (Bid Price), you will make a profit.