I'd suggest that, if you're really interested, you should get a beginner's book for Linux.
On the system level, Linux and Windows are mostly using the same concepts. The difference with Windows is that the low-level stuff is all hidden behind a graphical user interface, and often not accessible or only with great difficulty. With Linux the low-level stuff is accessible by the user (which is a good thing if you want to fix a problem yourself). This can often confuse new users, but it's not needed to get started.
The internet tablet, of course, is a consumer device and so Nokia put a user interface on top to be easily usable by everyone. Normal users would never see the Linux beneath. But if you want to leave the path of being a consumer who just uses the tablet for what it was advertised for, you can do so, because it runs Linux. The door to the powerful low-level layers of the tablet is the X-Terminal in the Utilities menu.
At a first glance, the X-Terminal appears to look and work a bit like DOS or cmd.exe in Windows. The command line is very powerful, if you're willing to dig into it, and the basic stuff is not very difficult. As a side-result you will also get to understand the basic principles of Unix, which can also be helpful when working with MacOS-X or Solaris or other Unix-style systems.

But we warned: Learning Unix takes some time.
But it never hurts to know the basic shell commands like 'ls', 'cd', 'rm', 'cp', 'mv', 'ln', 'ps', 'kill'. These few commands can already get you quite far.