Contracts are creatures of state law
What is a contract?
The basic elements of a contract offer, acceptance and considerations. This means that the parties must agree to the essential terms of the transaction, so that it is possible to say there is mutual assent, and they must exchange something of value, regardless of how minor this might be. Additionally, a contract is only enforceable if the parties have capacity, and there has been no duress, undue influence, mutual mistake or illegality.