Bid and ask are terms that describe the prices at which buyers and sellers are willing to trade a security, such as a stock. The bid price is the highest price that a buyer is ready to pay for a share. The ask price is the lowest price that a seller is willing to accept for a share. The difference between the bid and ask prices is called the spread, and it represents the profit for the market maker who facilitates the trade.

For example, suppose the current quote for a stock is $10.00 / $10.05. This means that the bid price is $10.00 and the ask price is $10.05. If you want to buy the stock, you will have to pay $10.05, which is the lowest price that any seller is offering. If you want to sell the stock, you will receive $10.00, which is the highest price that any buyer is bidding. The market maker who matches your order will earn $0.05 per share, which is the spread.