A Full Stack developer is a professional who masters both the frontend (what the user sees) and the backend (the system logic and databases). They are like the "all-rounder" of development, capable of building an application from start to finish. To do this, they need to know technologies such as HTML, CSS, and JavaScript for the frontend, and languages like Node.js, Python, or Java for the backend, in addition to databases and servers. It is a highly sought-after profile because they can handle complete projects without depending on other specialists.