DDE is a data generation tool that addresses challenges in testing like generating well-formed, consistent, reusable test data at scale. It allows defining generation rules independently and uses references, built-in functions, and custom Python functions to synthesize or extract multi-language data from various sources. The tool has a simple interface and makes it easy to create rule definitions, setup configurations, and generate positive and negative test data for performance, automation, and functional testing from external systems or basic data structures.