Our mentors and page authors are not necessarily lawyers. Even when they are, this page is not legal advice and they are not creating a lawyer-client relationship. You should consult a professional if possible and they can tell you whether this advice applies to your situation.
The main point of contract law is that what the parties agreed on goes. There are a lot of exceptions that you'd learn about in law school. You mostly don't care about those. A contract is just an enforceable deal, "I'm required to give you X for Y." That's all.
The contract is the agreement, not the document.
That piece of paper that says “contract” at the top? That’s just a record of what the agreement was. Usually there’ll be a clause saying “this document contains the entire agreement,” so that both parties know it’s an accurate record. But if you sign something and simultaneously say “we also talked about X in exchange for Y and I didn’t see those in there,” you do have a contract for both parts.
(Lawyers are now screaming at me about the parol evidence rule. This is one of those law school exceptions you mostly don’t care about. It might mean it’s very hard to prove there was more to the contract, but you weren’t planning on going to court.)
Or you could email someone a signed document, but give the same email a paragraph saying “hey, what does this part mean; I think it was ___.” If that happens and they don’t object, your version is true.
If something seems unfair, it probably is.
You get to count on people telling the truth and not hiding things. If someone breaks a deal, they owe you your money back plus enough to find someone else. You can alter a deal if both sides agree. And so on. Contract law (as written) actually goes out of its way to protect the non-expert side of a deal more than the side that is in the business, wrote the contract, or has lawyers.
If your contract is for services, like if you hired someone to re-pave your driveway, then you probably can’t actually make them do it. No matter how badly they broke the contract, forcing people to do things isn’t really an option on the table. What you are entitled to is some amount of money to even things out. If it’s a contract for goods, like if you tried to buy some object, then you can be entitled to get that specific thing.
Knowing your rights can help you.
No one actually wants to go to small claims court over a contract argument. If you can say “We agreed on X and the law is on my side because of Y,” probably they’ll eventually fold. It helps to be right. You can skim through the Uniform Commercial Code or the Restatement (Second) of Contracts for something that looks related. (Neither of these is actually the law, but they’re pretty reliable. Every state has passed something more or less like that.)
Wait, so what's up with "I agree to the Terms of Service"?
Yeah, those break every rule in the book. It’s a take-it-or-leave-it contract where no one bargained about it, one side can change it at any time, and the other doesn’t know what’s in it. The official stance of contract law is something like “try not to think about it,” but that’s what most of us were doing anyway.
If something in there is really unconscionable, you’d have a claim, but chances are the power of social media will act first because a ton of other people will be in the same position.