You are accessing a XAMPP installation installed on your local network, not on your mobile.
This could even happen with a device on which you can not install anything, such as a TV or an old cell phone.
The message Forbidden Access means that the installation has been modified and does not work the way you are accessing. The default would be to display / xampp information about the server. If you do not administer such an installation, or know what is installed or how to access it, you can at most guess the access: / xampp, / phpmyadmin, /login.php etc. - but nothing can be installed.
The utility is that it is a server, probably a development server. I do not know about your network, but it is capable of being in a public place and someone on this network has a server installed, or someone is testing things. For you it is of no use, but since XAMPP is probably not installed on your phone, it does not hurt you either.