LINUX is based on a directory and file scheme. Think of an upside down tree. When you want to access a drive you have to mount it. To disconnect the drive you have to un-mount it. DOS or Windows does this behind the scenes so you do not have to mount and un-mount drives. When LINUX mounts drives it links it to a directory. When you get mounting and un-mounting down, you can do almost unlimited things with it.
A few sites that helped me learn LINUX
The man or info pages are your friend. Use it as often as you like.
In any OS, do not be afraid to harm it. Make it a mission to crash it. Its the only way to learn a new OS.
BTW, you may want to get Knoppix just in case you went crazy trying to crash LINUX.