Ubuntu is a great OS but not for the faint of computer savvy hearts. The download file is an ISO disc image of nearly 700MB's. After downloading you need to burn it to a CD using the image option in the CD burning software if you want to boot from that for a new installation. This CD can also be purchased at most computer stores for about $1.99. This is a much more preferred option if available. You just need to be aware of harware requirements. If an old machine is barely running Win95, dont change it, you're might not find Ubuntu drivers for it (video, network, sound cards etc.).


As for file/folder structures, just think of how they are, or would be, in a file cabinet. Each drawer is a top folder each hanging tab is a sub folder, each file folder in each hanging tab is a sub-sub-folder and so on.