Let's say that X is interested in buying Y's house. Using a smart contract, the agreement to buy a home is made on the blockchain platform.
A deal between X and Y makes up the smart contract. The contract could say, "When X pays Y 30ETH, X will own the house."
Once the smart contract is written, no one can change the terms and conditions. So X feels safe giving Y ETH for the house.
Without smart contracts, X and Y would have to pay extra fees to third-party companies, lawyers, house brokers, and banks. You would no longer have to pay commissions and wait for a broker and a lawyer to handle your request.
With blockchain technology, this is now possible. Smart contracts can be set up so that they don't have to be handled by a central authority.