Database transactions are crucial for maintaining data integrity and consistency within a database system. Each transaction must be completed in its entirety or not executed at all; this is known as the atomicity property. Transactions are used to manage changes made to the database and are essential in scenarios like financial transactions, where it is critical that operations are completed successfully and are reversible if needed. Common properties that govern transactions are encapsulated in the ACID model, which stands for Atomicity, Consistency, Isolation, and Durability.