What is a transaction in the database?

1. A transaction is a series of operations performed as a logical unit, and a logical work cell must have four properties, called the ACID (atomicity, consistency, isolation, and persistence) attribute, in order to be a transaction:
Atomic Nature
2. The transaction must be an atomic unit of work, either all executed or not executed for its data modification.
Consistency
3. When the transaction is complete, all data must be kept in a consistent state. In a related database, all rules must be applied to transaction modifications to maintain the integrity of all data. At the end of the transaction, all internal data structures, such as B-tree indexes or doubly linked lists, must be correct.
Isolation of
4. Modifications made by concurrent transactions must be isolated from modifications made by any other concurrent transaction. The state in which the data is located when the transaction is viewing the data, either when another concurrent transaction modifies its state or after another transaction modifies it, and the transaction does not view the data in the middle state. This is called serializable because it is able to reload the starting data and replay a series of transactions so that the state at the end of the data is the same state as the original transaction execution.
Durability
5. After the transaction is complete, its effect on the system is permanent. This modification will persist even if a system failure occurs.

What is a transaction in the database?