UUID stands for Universally Unique Identifier. UUIDs are used as IDs (to identify) unique objects or records. These are very common in a big data environment where coordinating unique IDs in a central location is difficult to do. Most values (if not all) in a UUID are generated randomly (depending on UUID version).

UUID Format

UUIDs are simply 128 bit values, generally seen in hexadecimal form. A UUID is generally 36 characters long, with 32 hexadecimal values split into groups with 4 hyphens. You can see the UUID example below in this format 8-4-4-4-12:
123e4567-e89b-12d3-a456-d71b9123ae34

Possibility of Duplicates

UUIDs are not guaranteed to be unique, but it is very unlikely that two UUIDs will ever be the same. Especially within one system. There are a possible 2^128 unique UUID values. Wikipedia tells us that if you generated 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%.