Joint Application Development (JAD) is a process that accelerates the design of IT solutions through customer involvement and group consensus building. It involves continuous interaction between users, developers, and other stakeholders through structured workshop sessions. Key roles in JAD include the executive sponsor, project manager, end users, facilitator, and scribe. The process consists of defining objectives, preparing for sessions, and holding sessions to jointly develop solutions. JAD allows for faster development with fewer errors through collaboration and consensus between stakeholders.