RESTful API Modeling Language (RAML) provides human-readable and machine-processable documentation for your RESTful web services. It helps you to clearly document resources, methods, parameters, responses, media types, and other HTTP constructs that form the basis for a RESTful web service. RAML was first proposed in 2013 by RAML Workgroup. Today, RAML Workgroup includes technology leaders from various software vendors such as MulesSoft Inc., PayPal Inc., Intuit Inc., and Cisco.

RAML is built on standards such as Yaml Ain't Markup Language (YAML). YAML is a human-friendly data serialization standard that works with any programming language. If you are not familiar with YAML, go through the wiki page available at http://en.wikipedia.org/wiki/YAML.