The README file is an essential part of a free software package, providing users with key information about the package including the name, version number, description, installation instructions, and licensing details. Following the GNU Coding Standards, the README file should be easily visible in the distribution and written in a format that is easy to read on a text-only terminal. While traditional UNIX file extensions are minimal, using .txt or .md for Markdown files is acceptable. Complex markup languages like HTML should be avoided in the README file to ensure accessibility for all users. Overall, adhering to these guidelines helps create a clear and informative README file for software users.
https://softwareengineering.stackexchange.com/questions/301691/readme-txt-vs-readme-txt