A Full Stack Developer is someone who has a deep understanding of front-end as well as back-end development. So effectively, Full Stack Developers aren’t just well-versed with front-end technologies and UI/UX technologies such as CSS, Javascript, Angular, AJAX, etc., but also have expertise in back-end applications and database structures such as SQL, PHP, Javascript, C#, etc. While the front-end is what the user sees and uses, while the back-end involves the server-side processes such as database processes, user validation, etc.