If you are a web developer, you must have a program that can make your own computer or laptop to be able to handle HTTP request, because by default, your computer wouldn't be able to handle that. Try to open your favorite web browser, and access at http://localhost, it shouldn't work, you need a program that can make your computer to handle such a thing,  it commonly called HTTP Server. If you are running Windows, XAMPP is program you need.

It's because XAMPP is easy to install, easy to use and full package. You have all everything from not just HTTP but database system like MySQL or Maria DB, running PHP program and many other extra features. Basically XAMPP is just wrapper for Apache HTTPD, MariaDB  and PHP, it works by manage all that program to work and integrated altogether.

XAMPP Control Panel

It has control panel, so you don't need to open terminal and starting, reloading, restarting, stopping your HTTP server, you can just using GUI. The GUI is so simple, but it already has everything you need to work with your web development process.

XAMPP is not production ready, it is not good at handling bigger transaction, it's so slow and can be crash anytime. So after the development process finished, you need to deploy your program to specific HTTP server, it can be Apache, Nginx or other production ready HTTP Server.

To download XAMPP, you can go to https://www.apachefriends.org/download.html