This is the slickest app I’ve seen/used yet to create bootable usb flash-sticks (aka ThumbDrives, PenDrives, etc.). Easy install, and even easier operation.
Etcher is “Cross-Platform”, . . so, works great on your Windows or Ubuntu PC’s/partitions.
Why bootable thumbdrives? For rescue media . . that allows you to access and save your important files OR to provide a way to install or run another OS on your PC (without changing your current setup).
So, when a Windows PC goes “BSOD” (blue screen of death) and our local Windows guru is on an extended vacation, you’ll still have a functional secure PC!