At this point the offer becomes a legally binding contract on all parties. The buyer takes on certain obligations to see the sale through and the seller gains certain legal rights to hold the buyer to the offer. The next stage is negotiating and signing the purchase & sales agreement. People enter into contracts daily without even thinking about it—when we fill up with gas, go to the hairdresser, sign up for a gym membership, etc. So, what exactly is a contract? It’s an agreement between two or more parties: one party accepts what the other party has to offer, in exchange for something else.