Data consistency refers to the accuracy and reliability of data across a database or system. It ensures that the same data remains uniform and unchanged, regardless of where it is accessed or modified. For example, if a user's information is updated in one part of a system, it should reflect the same changes everywhere else, maintaining integrity. In databases, data consistency is crucial for operations like transactions. When multiple users interact with the same data, mechanisms like ACID properties (Atomicity, Consistency, Isolation, Durability) help maintain consistency. This prevents issues like data corruption or conflicting information, ensuring users can trust the data they see.