A contract is an agreement entered into between two (or more) parties with the intention of creating legally binding obligations as recognised by the law.
For a contract to be binding, it does not have to be in writing. An oral or verbal agreement is equally binding. The problem with verbal agreements is that the parties do not have proof of the terms of the contract.
An attorney does not have to draft or review a contract for it to be legally binding. However, if a person drafts his own contract without the assistance of an attorney, he has no assurance that it will be legally binding if a dispute arises. Therefore, it is not wise or good business practice for parties to draft their own contracts without the assistance of an attorney.