I'd recommend you dive right into Linux by installing an
easy-to-handle Linux distribution. (You could start with SuSE Linux,
http://www.suse.com, which aims to be much like M$ Windoze.)
SuSE - and I think also other distributions - has a nice online help
in their help system which includes an introduction to Linux for users
as well as administrators, both available in several languages.

Otherwise look for "Linux Tutorial" or "Linux Howto" or "Linux mini
howto" or "introduction to Linux" with Google and/or on Amazon.com (or
whatever online bookstore you like). I don't know if "Linux for
Dummies" is a good book, you could look into that too.
(I've found this English tutorial online (which is quote old though):

If you are interested in the way the file system is organized try to
understand the "Filesystem Hierarchy Standard". (Look for "linux file
system standard" with Google, the first 3 hits are your friend!)
I think this is the official site: http://www.pathname.com/fhs/

Hope that helps.