XAMPP for Windows, macOS, and Linux is a completely free, easy-to-install Apache distribution containing MariaDB, PHP, and Perl.
Many people know from their own experience that it's not easy to install an Apache web server, and it gets harder if you want to add MariaDB, PHP, and Perl. The goal of XAMPP is to build an easy-to-install distribution for developers to get into the world of Apache.
To make it convenient for developers, XAMPP is configured with all features turned on. In the case of commercial use, please take a look at the product licenses; from the XAMPP point of view, commercial use is also free. There are currently distributions for Windows, Linux, and OS X.