Final answer:
A GUID is a 128-bit number used to ensure that objects such as files, users, or system resources have unique identifiers across systems and networks.
Step-by-step explanation:
A GUID (globally unique identifier) is a 128-bit number that ensures that no two objects have identical names. In computing, a GUID is often used to identify objects such as files, users, or system resources, with a high assurance that the identifier is unique not just within the local system, but across multiple systems and even different networks. Each GUID is mathematically generated to create a very large number of possible identifiers, making it extremely unlikely that two GUIDs will be the same, thus ensuring uniqueness. This system is particularly important in large-scale distributed systems where objects or data need to be uniquely identifiable across various components and services.