Transactions are the safety net of the database world. They allow you to group complex operations together so they behave as one single, unbreakable unit.
1The All-or-Nothing Rule
Atomicity is the 'A' in ACID. It means that if a transaction has 10 steps and step #9 fails, the database will undo the first 8 steps for you. You never end up with 'half-finished' data.
2Isolation Levels
Databases are busy. Thousands of people might be changing data at once. Transactions ensure that your work stays 'Isolated' from others until you are ready to reveal it with a COMMIT.
3Consistency & Durability
Once you COMMIT, your data is 'Durable'—even a total hardware failure right after won't lose your data because it was written to a transaction log first.
