A README file, typically named README.txt or README.md, is a plain text file that provides information about a software project or a code repository.

It is usually the first file a user will see when they access the code or the repository, and it provides a brief description of the project, its goals, how to install and use it, and often includes a list of contributors and resources for further reading. The README file serves as a guide for those who are new to the project and provides a high-level overview of what the project is about and how it works. In many cases, it can also provide a quick reference for developers who are already familiar with the code. The README file is an important component of open-source projects, as it helps to make the code more accessible and easier to understand for the community.

The original Bitcoin README file was created to provide an overview of the Bitcoin software project when it was first released. It was a plain text file that described the purpose of Bitcoin and provided information about how to download and run the software.