ISO image is a term commonly associated with CD and DVD burning. An ISO image (or .ISO file) is a computer file that is an exact copy of an existing file system. An ISO can contain the entire contents of a CD-ROM disc or CD medium. ISO files are typically created through a software application that will open, create, edit, and extract CD or DVD image files, then convert the extracted image to an ISO file, easily allowing users to burn an exact copy of the original onto CD or DVD.
He got a leaked version of the xbox iso which was burned to a cd and sent to him. With some googling I could probably find the game and download the iso + burn it and play it on an xbox 360 with cracked firmware.
Google how to flash your Xbox 360 firmware. It allows you to run backups on your Xbox. That way you can download the ISOs of any game for the 360 and burn it to a dual layer dvd and play it on your xbox without adding a modchip. Yay.
Unless you're completely computer illiterate you won't break anything.