ACID (an acronym for Atomicity Consistency Isolation Durability) is a concept that every database management system must strive to achieve. For a reliable database all these four attributes should be achieved.
Atomicity: stats that database modifications must follow an “all or nothing” rule. Each transaction is said to be “atomic”. If one part of the transaction fails, the entire transaction fails.
Consistency: stats that a transaction either creates a new and valid state of data, or, if any failure occurs, returns all data to its previous state. It means a transaction will never leave your database in a half finished state.
Integrity: keeps transaction separated each other until they are finished. A transaction in process and yet not committed must remain isolated from any other transaction.
Durability: ensures that any transaction committed to the database will not be lost. Committed data are saved by the system in such a way that, even in the event of failure or system restart, the data is available in its correct state.