YAML (YAML Ain't Markup Language) is a human-readable data serialization standard that can be used in conjunction with all programming languages and is often used to write configuration files. It uses indentation to denote scope, making it cleaner and more readable than JSON or XML. YAML is heavily used in DevOps tools like Docker (Compose), Kubernetes, and Ansible for defining infrastructure as code. YAML sample files are used to test configuration parsers and deployment scripts. Developers use them to verify interpretation of scalar values, lists, and dictionaries. Since YAML relies on strict indentation, samples with various formatting styles are used to test the robustness of parsers and to detect syntax errors before they cause deployment failures.