The UUID (or GUID) is a 128-bit serial number that is generated using time and a process called hashing. Each UUID (Universally Unique IDentifier) has a unique combination of numbers and letters, giving it the nickname "GUID" (Globally Unique IDentifier). The purpose of the UUID is to identify an object uniquely; this can be accomplished because objects can change their state. A computer system would use this data to store information about updates, making it easier for users to retrieve old documents.
A UUID/GUID is 16 hexadecimal groups of 4 characters. It is the product of an algorithm that takes a 128-bit value and converts it into a 64 character string. The GUID format is not case sensitive, so "abcd" can be converted to "ABCD". GUID is typically used as a unique identifier because the probability that two strings will be the same is 1 in 2^128.
The UUID, being a unique identifier number, is a 128-bit random number that serves as a universally unique identifier. These numbers are typically used to identify objects without any identifying information. The more data an object has associated with it, the higher its chances of being tracked and identified by a third party. As a result, many programmers prefer to use UUIDs for objects that do not have any other identifying information.
There are many uses for GUID or Globally Unique IDentifiers. These include keeping track of important data in a system, finding duplicates within a system, and more. For example, an organization may use GUIDs to identify the location of a document on their network. This way, if there is ever confusion about where the document resides, they can go to their computer and trace it back to see where it's stored. Some programs also use GUIDs to identify duplicate files.