What are ACID transactions in databases?

ACID is a set of properties of database transactions that ensure reliability and correctness of operations:

• Atomicity: a transaction is completed in full or not at all. If something goes wrong, all changes are rolled back.
• Consistency: a transaction transforms the database from one valid state to another, adhering to 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 in the database and are not lost even in case of failures.

For example, when transferring money between accounts:

1. Deduct the amount from one account.
2. Credit the amount to the other account.

If an error occurs at any stage, the transaction is rolled back to prevent partial changes.