Front ends are just the main physical/visual components we see on the screen of a web app/page.
That should not be a problem to you to understand. Any device that has a browser can run/display *CSS which is actually a single file and or an embedded structure inside an HTML file. And it this CSS that does all the Painting work for HTML file, whether the file is local on the device where the CSS and HTML files were created or remote device in another planet running a reachable HTTP/FTP Web Server. To start learning how to program fullstack you really must want to be a programmer already after all.
Take for instance Java which is not a scripting language like Python and PHP can actually and must be compiled before using the code which compiles to a programme file which is a binary for JVM.
Just for the Memes
Java Prince Embedded