RAML (RESTful API Modeling Language) is a YAML-based language used to describe RESTful APIs. It provides a structured, human-readable way to define the resources, methods, parameters, and responses of an API. By using RAML, developers can design APIs in a way that is both machine-readable and easy for humans to understand, facilitating better collaboration between front-end and back-end teams. RAML supports modularity through the use of includes, traits, and resource types, which helps in reducing code duplication and maintaining consistency across large API projects. It is widely used in the software development lifecycle to generate documentation, create mock servers for testing, and even generate client-side SDKs or server-side boilerplate code. Because it is built on top of YAML, it is highly expressive and allows for complex data modeling, making it a popular choice for enterprise-level API design and governance.