A database transaction is a unit of interaction with a database management system or similar system that is treated in a coherent and reliable way independent of other transactions. In general, a database transaction must be atomic, meaning that it must be either entirely completed or aborted. Ideally, a database system will guarantee the properties of Atomicity, Consistency, Isolation and Durability (ACID) for each transaction. In practice, these properties are often relaxed somewhat to provide better performance.
In some systems, transactions are also called LUWs for Logical Units of Work.

Purpose of transaction
Databases that support transactions are called transactional databases. Most modern relational database management systems fall into this category.