ACID is an acronym that stands for atomicity, consistency, isolation, and durability. Together, ACID properties ensure that a set of database operations, grouped together in a transaction, leave the database in a valid state even in the event of unexpected errors.
Atomicity
Atomicity guarantees that all of the commands that make up a transaction are treated as a single unit and either succeed or fail together.
Consistency
Consistency guarantees that changes made within a transaction are populated across the database system (e.g. nodes) and in alignment with DBMS constraints.
Isolation
Each transaction is isolated from the other transactions to prevent data conflicts. If two users are trying to modify the same data, the DBMS uses a mechanism called a lock manager to suspend other users until the changes being made by the first user are complete.
Durability
Durability guarantees that once the transaction completes and changes are written to the database, they are persisted.