They are normally supported by back-end web developers, who are responsible for server-side application logic and integration of the work front-end developers do. Just choose one thing and become good at it and if you choose to become front end developer make sure you become excellent at it. There's more to front-end development than building a web site.
When starting out in front-end, you might not be sure where to start. There are so many options available not only programming language-wise, but regarding tools, frameworks, and technologies as well. So make sure to be prepared of open sea.
“Front-end development is like an ocean. You happen to have a ship, but no map. First learn the shallow waters and then go deep”