"The data on a computer is organized into ordered bytes like the file cabinet, and telling a program to go to some byte's location plus some offset can result in it accessing data that it shouldn't touch, if other safeguards aren't in place."
That's a great analogy, by the way.
This is the way one uses the 'buffer overflow' problem in computers to manipulate data. With a little skill you can use it to do serious damage. Consider, for instance, what would happen if we were at an engineering company and slipped in a new blueprint for a machine instead of a personell note. Later someone else would pick up the design and the factory, none the wiser, would proceed to build our machine, instead of the one they wanted.
- We agree I'll give you max 1L of water, so you prepare a 1L bucket. Then I pour 2L of water into your bucket - you end up with a mess. (exploit version: We agree that if any water hits the ground, I can force you to do anything.)
- I give you card with typical form to fill in (squares for every letter). First 5 squares are for first name, next 5 are for last name. You fill in "Michael" as your first name overflowing into last name space.
- etc...
Sure, it doesn't capture all intricacies of the mechanism, implementation, side effects of the overflow, etc. But don't tell anyone they wouldn't understand the concept.