What does the ACID principle in database transactions mean?

The ACID principles describe the properties of transactions in databases that ensure reliability and data integrity:

• Atomicity: a transaction is completed in full or not at all. If something goes wrong, all changes are rolled back.
• Consistency: after a transaction, the database remains in a correct state, satisfying all rules and constraints.
• Isolation: concurrent transactions do not affect each other, as if they were executed sequentially.
• Durability: after a transaction is committed, changes are saved and not lost even in case of failures.

Example: when transferring money between accounts, a transaction guarantees that the debit and credit happen together or not at all, maintaining data integrity.