Image file -
An ISO file (often called an ISO image), is an archive file that contains an identical copy (or image) of data found on an optical disc, like a CD or DVD. They are often used for backing up optical discs, or for distributing large file sets that are intended to burned to an optical disc.
www.howtogeek.com
Its how windows installer drives are made as well.
just watch video, he shows it all.
Burning the image makes the USB bootable and sets it up so as soon as pc starts from USB, it will run the program. You don't have to do anything
to boot off drive once its made
put USB in PC
go to settings/update & security/recovery
Under advanced startup, click restart now
PC restarts into a blue screen
choose use a device
pick USB from list
PC will restart and boot USB