This document provides an introduction to Azure DocumentDB, a NoSQL database service. It begins with an overview of the differences between SQL and NoSQL databases, focusing on how DocumentDB is a non-relational, horizontally scalable database that uses JSON documents. It then describes key aspects of DocumentDB such as its supported languages and frameworks, its HTTP REST API, how data is stored in JSON documents, and its resources and hierarchical structure. The document also covers querying data using SQL and the services' indexing and consistency capabilities.