The first question that must have come to your mind is, why do we even need a smart contract?
To understand that, consider that you are buying a property for which you need to request a mortgage loan from your bank. Funds approvals and deposit is a multi-step process that involves many parties and lots of regulatory paperwork.
You will have to fill in your personal information, contact all the intermediaries involved in the transaction, get signatures and so on. This not only consumes a tremendous amount of time but also adds up to the total cost considerably. And all of this because there is a lack of trust between the transacting parties.
Fast forward to the future when smart contracts are mainstream, and you are planning again to buy a property by taking a loan from a bank. You will be able to verify your identity using your digital identity stored on the blockchain. From the loan approval to the transfer of ownership, every successful transaction will be transacted in the matter of minutes and recorded on the blockchain.
This is how smart contracts eliminate the need for trust and make transactions faster and more secure.
More detail: https://theblockbox.io/what-is-smart-contract/