In Puppet, which file extension is commonly used for class definition files?

In Puppet, class definition files are primarily written using the .pp file extension, which stands for "Puppet manifest." This extension is specifically designed for Puppet's language, allowing it to recognize and properly parse the content within the file. The class definitions, resources, and statements are formulated using Puppet’s Domain Specific Language (DSL), and the .pp files serve as the core building blocks for Puppet configurations.

The other options represent different purposes or languages. JSON and YAML are data serialization formats often used for configuration files or settings, but they are not specific to Puppet class definitions. The .rb extension is associated with Ruby scripts, which Puppet is built upon, but it does not pertain to class definitions directly. Therefore, the use of the .pp extension is critical for conveying the required instructions and structure that Puppet needs to manage configurations effectively.