Full-stack web application development involves designing, building, and maintaining web applications that include both front-end and back-end components. The front-end refers to the user interface that users interact with, while the back-end includes server-side programming and database management. Full-stack developers are proficient in multiple programming languages, frameworks, and technologies, and can handle both client-side and server-side development. They work with tools like HTML, CSS, JavaScript, PHP, Python, Ruby on Rails, and more to develop fully functional web applications that meet the needs of businesses and users.