The .mustache file extension is used for templates written in the Mustache templating language. Mustache is a logic-less template system, meaning it aims to separate presentation from logic. It works by replacing tags in a template with values provided in a data structure (usually a JSON object or a hash). The template contains variables enclosed in double curly braces (e.g., {{name}}) which are replaced with corresponding values from the data. Mustache supports basic features like variable substitution, section rendering (for iterating over lists or conditional display), and partials (reusable template snippets). Because of its simplicity and language-agnostic nature, Mustache is widely used for generating HTML, configuration files, source code, and other text-based formats. Its logic-less design promotes cleaner code and easier maintenance, as the template focuses solely on presentation while the application handles the data manipulation and logic. The format is designed to be human-readable and easy to learn, making it a popular choice for both front-end and back-end development.