In trading and investing, the bid is the amount a party is willing to pay in order to buy a financial instrument. It is the opposite of an ask, which is the price that a seller will take in order to part with a financial instrument.
Bids usually comprise two elements: the price which the buyer is willing to pay, and the quantity of the financial instrument they are looking to purchase. A trade is executed when a matching bid and ask are combined. For example, a trader bidding $100 per share for 100 shares in Apple will see their trade executed when a seller agrees to that price and level.