the difference between front-end and back-end
A website itself is made of front-end part and back-end part.
In front-end, there are roughly three languages (honestly html and css are not programming languages). HTML is a structure of the website, CSS is a design aspect, and Javascript creates moving features in their website.
In Javascript section, they have Vanila.JS which is a pure Javascript, and also have some frameworks, such as React and Vue.
In back-end, they manage the behind of websites, it is invisible. They roughly have database (MongoDB, Mysql), cloud (AWS, Azure), and back-end software (node.js or .NET).