Hex editing is basically what every hacking tool does. I might say binary editing, actually. But no one does binary editing because it's so time-consuming. You know how computers run strictly off of a series of 0s and 1s, right? So that's binary. Any file on the computer, including ROMs, are stored as a series of 0s and 1s. Hexadecimal is just a representation of Binary, allowing you to type two characters instead of 32. Hacking tools are based off of editing the Hex, so it all comes down to how the file exists on the computer.