It can be money, property, a promise or even the agreement not to do something. For instance, when you buy a candy bar at the convenience store, the candy is the consideration given by the store and the purchase price is the consideration you give. Likewise, if a person agrees not to sue another for a sum of money, the promise not to sue is the consideration given. This does not mean that the consideration must be of equal, or close to equal value. If the buyer and seller are willing, a Rolls Royce can be sold for a nickel.
Consideration can also come from a third party.
Suppose, after an auto accident, the injured party agrees not to sue the other driver in exchange for a sum of money. Even though the money comes from an insurance company or the other driver's parents, the agreement is still valid and binding. There is a statute in Oklahoma that expressly allows contracts between husband and wife. There are limits to what a husband and wife can agree, however. After marriage, the ability of spouses to contract for the disposition of property or child support are subject to revision by a divorce court.