Consideration is an essential element of a valid contract. It refers to something of value that is exchanged by both parties to the contract. For example, in a sale agreement, the consideration for the seller is the money received in exchange for the item sold, while the consideration for the buyer is the item received in exchange for the money. Consideration must be real, lawful, and there must be a quid pro quo (something in return) between the parties. There are some exceptions where consideration is not required, such as natural love and affection between parties in a close relationship or time-barred debts.