A Full Stack Developer or engineer is a programmer who works within software development and implements an application using both the front-end and back-end technologies. Their main job is to create a seamless user experience using their diverse skill set. They're also proficient in databases, server configuration, user interface, and many more. It's important to note that as a full-stack developer, you don’t need to know everything, but need be familiar with what's going on in the front-end and back-end is key.
If you want to become a full-stack developer, check out this Full stack Developer Course by Intellipaat.