A full stack developer is responsible for designing, developing, and deploying web applications, handling both the client-side and server-side components. They have a comprehensive understanding of various programming languages, frameworks, and tools required for building robust and scalable applications. Full stack developers are proficient in front-end technologies, back-end technologies, and databases, allowing them to work on different layers of the application stack. They are adaptable, versatile, and capable of taking on various roles within a development team.