A full stack developer isĀ a web developer or engineer who works with both the front and back ends of a website or application. In this sense, they provide an end-to-end service, and can be involved in projects that involve databases and building user-facing websites.
Learning full-stack development will help you master a wide set of skills ranging from HTML, CSS, JavaScript, back-end languages (Python, PHP, Ruby), database storage, HTTP, REST, and NPM, along with a good set of Agile project management and soft skills.