Smart contracts are computer programs or protocols for automated transactions that are stored on a blockchain and run in response to meeting certain conditions. In other words, smart contracts automate the execution of agreements so that all participants can ascertain the outcome as soon as possible without the involvement of an intermediary or time delay.
A smart contract is a sort of program that encodes business logic and operates on a dedicated virtual machine embedded in a blockchain or other distributed ledger.

The contract is immediately executed when a condition is met. Because smart contracts are digital and automated, there is no paperwork to deal with, and No time was spent correcting errors that can occur when filling out documentation by hand.
Because blockchain transaction records are encrypted, they are extremely difficult to hack. Furthermore, because each entry on a distributed ledger is linked to the entries before and after it, hackers would have to change the entire chain to change a single record.