The Spread Is The Difference Between The Bid And The Ask Prices For A Security. When Buying Or Selling A Security, The Spread Represents The Cost Of A Transaction. The Bid Price Is The Price A Buyer Is Willing To Pay For The Commodity Or Security. Designed As A Chart, The Bid Represents The Highest Price A Buyer Is Willing To Pay. The Ask Price Represents The Lowest Price A Seller Is Willing To Sell A Security Or Commodity. Designed As A Chart, The Ask Represents The Lowest Price A Seller Will Accept.