My Cents. (Score 2, Insightful)

I think that the best way to explain something to someone who has absolutely no idea what you are talking about is to use metaphores and / or analogies. For example, to explain how the file structure works: "Think of your computer's hard drive as a filing cabinet. In a filing cabinet, you have individual drawers, and inside of the drawers you can have green folders, and inside of those folders you can have vanilla folders. Your hard drive is almost exactly the same, the main differences being that it can store much more then a filing cabinet, and that you can have an infinite amount of nested folders." Or, you could go with the tree aproach, and explain that the main trunk is the drive, and each branch is a folder, and each leaf is a file, and maybe have a picture of a tree, but with the trunk / branches / leaves labled.