With all of the talk lately about Maemo and Andriod and other Linux based OSes, I just had a few newbie questions.

Is Linux technically an OS or a type of computer language, since there are so many different Linux distros?

If Linux is an OS, then how is it that there are so many different kindsof Linux distros? And on that note, what is the difference between Debian, Symbian, Maemo, and Android, since they are all based on the same Linux?

If a device has one OS, is it possible to install another different OS on there (ie. Motorola Droid comes with Android, can it be flashed to run Maemo)? If not, why is that?

I've been reading up on the Maemo vs. Android debate and a recurring theme is that Maemo is more "open." How is Maemo more "open" when both Android and Maemo are Linux based, which is completely open?

Lastly, how is it possible that Linux is capable of running on both x86 architecture devices and ARM architecture devices? Isn't the x86 and ARM instruction set completely different? And if I'm not mistaken, Linux is also used in PowerPC machines too.

Thanks for your help!