Kylix is Borland's Delphi ported to Linux. It allows code you write in Linux to be very easy to port to windows and vice versa. Its a Rapid Application Development suite and therefore has the form generation bits there (drag and drop componants) as well as the language and the IDE.
In the latest versions it also has a c++ version tagged on as well which allows the same style development but with the c++ language instead of delphi. One thing to note about the c++ version is that the documentation is no way as good as the delphi documentation. But there are a number of sites on the net so.
Try looking on about.com for loads of programming help sites.
Posix is entirely different thing. Look here http://www.everything2.com/index.pl?node_id=36633
for some good explanations.