DSDM is an agile framework for rapid application development that originated in 1994. It focuses on iterative development and user involvement to deliver working software quickly. The DSDM process involves pre-project planning, iterative development cycles of functional modeling, design, and building, and post-project maintenance. Key principles include empowering teams, frequent delivery, addressing current needs iteratively, and ensuring changes can be reversed. Critical success factors include management commitment and supportive relationships between users and developers.