ACID properties ensure database reliability:

• Atomicity: Transactions are all-or-nothing. If any part fails, the entire transaction rolls back
• Consistency: Database remains in a valid state before and after transactions
• Isolation: Concurrent transactions don't interfere with each other
• Durability: Committed changes persist even after system failures

Example:

BEGIN;
UPDATE accounts SET balance = balance - 100 WHERE id = 1;
UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT; -- Both operations succeed or both fail