ACID Properties

ACID is the set of properties that make database transactions reliable: Atomicity, Consistency, Isolation and Durability. A transaction is a group of operations that should succeed or fail as a whole, such as moving money between two accounts.

Atomicity means all steps happen or none do. Consistency means a transaction moves the database from one valid state to another, respecting all rules. Isolation means concurrent transactions do not interfere with each other. Durability means once a transaction is committed, it survives crashes and power loss.