Apache HTTP Server (or Apache) is the world’s most widely used, open source web server. Basically, when a browser asks for a web page, it processes the request and sends the website back to the browser – just like any other web server.
Current versions can run on Linux, Unix and Windows systems. It has many features from URL rewriting to virtual hosts and it has many extra modules to extend core functionality.
The easiest way to try it is to download XAMPP, which will install Apache along with other things like PHP and MariaDB, so you can jump right into the middle of web development. It also gives you an easy-to-use interface, where you can turn things on/off with a button.