PS：It’s not the exactly answer for anything.But it can help us know something though the example.
Content of a contract：
A contract is a valid offer which is accepted by another party based on a pure and free consent. The offer should be clear, direct and unequivocal. A contract can create by two or more parties who should have the legal capacity. The object of a contract is the heart of it. It can’t be violated by legal, moral and public policy.
Elements of a contract：
A valid offer and acceptance
The contract should have an offer, sometimes more than one offer to another party who should accept this offer. For example, a seller sells his car for $2000, and the buyer accepts the price. But be careful that a counter-offer isn’t a acceptance. If the buyer doesn’t agree for the price and asks for $ 1600, it is another offer. If the seller agrees for the new price, the contract will be created.
A mature consideration
It means the parties should exchange some value. As the same example, the buyer will get the car, and the seller will get the money.
Legal capacity of the parties
Legal capacity is used to define that these parties are able to understand and appreciate the consequence of his action. It involves his age and mental condition.
Good faith by the parties
It is means that the contract is clearly intended by its parties. For example, the buyer wants to buy a car, the seller couldn’t think that I can sell my toll car to him.
Legal subject matter
The legal subject matter shouldn’t have the criminal intent.