Spread

What is the spread?

The "spread" is the difference between the "bid" price and the "ask" price on over-the-counter market securities. The term "bid" refers to the highest price a market maker will pay at any given time to purchase a specified number of shares of a stock. The term "ask" refers to the lowest price at which a market maker will sell the stock.

The ask price (also known as the "offer" price) will almost always be higher than the bid price. Market makers make their money on the spread. (Source: SEC)

The bid/offer spread (also known as bid/ask spread) is the difference between the buying (bid) and selling (offer) price of the same transaction (eg stock, futures contracts, options, currency).

The ask (offer) prices are immediate execution (market) prices for quick buyers (ask takers); bid prices for quick sellers (bid takers). If a trade is executed at market prices, closing that trade immediately without queuing would not get you back the amount paid because of the bid/ask difference. (Source: Wikipedia)