The folders you see when you connect your Kindle to your computer are simple simple simple.
It doesn't matter if you connect your Kindle to a pc or a mac. The folders are going to be the same. After all... your Kindle isn't dependent on a Windows or a Mac operating system. It has its own operating system, and when you connect it to your computer, as far as your computer is concerned, you just connected an external hard drive.
The documents folder is where your ebook files should go. Anywhere else, and you aren't going to be seeing them on the home screen of your Kindle.
Any book files (files you know for sure are yours) that accidentally end up outside these folders can be safely deleted. If you put them there, you can take them out. Just don't go deleting anything you aren't sure of. My only rule is... If you didn't create it yourself, or you don't know what it is... DON'T DELETE IT. I'm not big on hard and fast rules, but I live by this one.
The audible folder is where you can put audio book files, or any mp3 music files you want to manage and listen to on your Kindle with some control. Mp3 files places in this folder will appear on your Kindle home screen and can be organized into collections just like your books. When you "play" one of these files, you will see actual controls you can use to stop, pause, fast forward, etc using the 5-way controller on your Kindle. The same thing applies to this folder... if you stick those audio mp3 files anywhere else, you are not going to see them on your Kindle home screen. I'm not sure how the controls will work on the new Kindle Fire, but I'm sure looking forward to shaking it down and finding out.
The music folder is for down and dirty m3 music files. Music files placed in this folder can be played in the background while you are reading. You don't really have any control over the order in which they are played. The Kindle will simply play them in the order they were loaded onto your Kindle. Remember... if you put mp3 files anywhere else, your Kindle will just ignore them. To play music in the background your files must be in this music folder.
The keyboard commands to play music on your Kindle are:
Music playback:
- alt+<space>: play/pause music. Also pauses spoken text function.
- alt+F: forward to next music track