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
http://www.justlinux.com
http://www.tldp.org/
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.