Like when you buy a house, you sign a purchase contract, give it to the seller. That's an offer. Multiple parties can do this and the seller would have multiple offers. The offers do not bind the buyers until the seller choose one offer and signs that paper, then that and only that offer becomes a contract.
You cannot go to court with a paper containing only signature from the other party and enforce it. You have to add your signature before the contract is valid. In another word, you can't have a contract only binds the other party but not you. You can't have your cake and eat it too.
