A Universally Unique Identifier (UUID) is a 128-bit number used to uniquely identify information in computer systems. It is designed to ensure that no two UUIDs are the same, even if they are generated in different locations or at different times. This uniqueness is crucial for applications like databases, where distinguishing between records is essential. UUIDs are often represented as a string of hexadecimal digits, typically displayed in five groups separated by hyphens. They are widely used in various technologies, including databases, web services, and software development, to provide a reliable way to identify resources without requiring a central authority.