Yellow Paper is a term that refers to an official technical specification document that describes the design, operation, and implementation of a blockchain protocol in a detailed and formal manner, written in a mathematical academic style.

The Yellow Paper is the ultimate reference document for an in-depth understanding of how a blockchain protocol works. It provides a comprehensive explanation of all aspects of the protocol, including data structures, code execution, consensus mechanisms, and more, in formal language and rigorous mathematical notation.

While the use of such language and notation may be unfamiliar to most programmers, the Yellow Paper is intended to be the official and authoritative source for understanding how blockchain protocols work technically. It serves as a reference specification for developers, researchers, and anyone else who wants to delve into the internal details of the protocol in depth.

A Yellow Paper is typically written by the founder or lead developer of a blockchain protocol, and is often updated by other contributors over time to reflect changes or updates to the protocol. Yellow Papers are often licensed under open licenses such as Creative Commons, which allows them to be freely used, distributed, and modified, provided proper attribution is given.