Could you explain what is meant by a transaction in the context of working with databases?

A transaction in databases is a sequence of operations that is executed as a single unit. It has four main properties (ACID):

• Atomicity: all operations within the transaction are either fully completed or not executed at all.
• Consistency: after the transaction completes, the database remains in a correct state.
• Isolation: concurrent transactions do not affect each other, as if they were executed sequentially.
• Durability: after a transaction is committed, its changes are saved even in case of failures.

Example: when transferring money between accounts, a transaction guarantees that the debit from one account and the credit to another happen together or not at all, to prevent losing money or creating an excess balance.