Legal Question in Civil Litigation in California

With certain exceptions, yes. A contract is not a piece of paper. It is an agreement that has certain characteristics that make it legally binding. Some contracts are of such importance that they will not be enforced unless they are evidenced by a written document, and some are so important that only a written document signed by the person to be bound to it are enforceable. There are specific code sections that state what contracts must be in writing and whether they must be signed. Otherwise they may be written or verbal. Also, when a contract is only verbal, you only have two years to sue for a breach; whereas you have four years for a written contract.

I agree with Mr. McCormick. The only point I would add is that it can be much more difficult to prove the existence of an oral agreement if you have to go to court.

Mr. McCormick's answer is accurate but incomplete. He's right that most types of contracts don't have to be written. But not every agreement qualifies as a contract. Even written agreements often don't qualify. An agreement must meet certain requirements in order to be a valid contract.

The advantage of written agreements is that they make it harder for the parties to later dispute what they agreed to. Proving the details -- or even the existence -- of an oral agreement can be very hard. But whether you have a valid contract is a different question from whether you can prove it.

Binding means that you will be able to enforce your 'deal' it in a dispute, through admissible evidence and testimony that proves all the required elements and terms of the 'deal'. How do you plan on doing that in a dispute over 'who said what'?