Perhaps they referenced this guide to create a bootable Live USB on Windows, allowing them to test drive something like Ubuntu without making any changes to their PC.

Create a bootable Linux USB from macOS Plug the USB drive into your Mac system and open the Terminal app (just search for Terminal in Spotlight).

Create Bootable Installation Media To boot, try, and install the Linux system you downloaded, you'll need to create bootable installation media from your ISO file.

How to make a bootable USB drive If you're trying to install a new operating system or flash your BIOS, you're going to need a bootable USB drive - here's how to make one.

There you have it — a bootable copy OS X Mavericks on USB Flash Drive that can be used to install, upgrade, and/or troubleshoot compatible Apple computers.

Jesus Vigo goes over the steps to create a bootable USB to install OS X 10.7-10.8 and OS X 10.5-10.6, as well as how to put multiple versions on the same USB.