It might be a silly question, but seriously is everything in Ruby works in Rails?
I mean is that rails did not overwrite anything, but just added new things to ruby, right?
(Sorry for the silly question. I just learnt rails for about 4 months and no any experience in ruby yet (except rails ;D)).
Rails is just a framework written in ruby, so in principle you should be able to use any library, class or module you want to. However not everything makes sence, like GUI frameworks etc.
The ruby implementation and platform you’re running on may also have limitations, like everything may not work on a windows server, or on MacRuby or JRuby etc.