UUID, which stands for Universally Unique Identifier, is a standardized identifier format used in software development to generate unique identifiers. UUIDs are designed to be globally unique across space and time, meaning that the probability of generating the same UUID for different entities is extremely low.

UUIDs are typically represented as a 128-bit value, usually displayed in hexadecimal format and separated into five groups, such as "8-4-4-4-12". The uniqueness of UUIDs is achieved through a combination of factors, including the timestamp of creation, a unique identifier for the generating host, and randomness.

There are several versions of UUIDs, each with different algorithms for generating the identifier. The most commonly used version is UUID version 4, which relies solely on randomness to generate the UUID.

UUIDs are widely used in various contexts, including database keys, distributed systems, messaging systems, and network protocols. They provide a convenient and reliable way to generate unique identifiers without relying on a centralized authority.

One of the main advantages of UUIDs is their universality, meaning that they can be generated by any system without coordination with other systems. This makes them particularly useful in distributed or decentralized environments where coordination may be challenging.

Overall, UUIDs are an essential tool in software development for ensuring uniqueness and avoiding collisions when generating identifiers.