Also want to know, what is the flavour of UNIX means
Unix comes in many different versions under various names. Suns version is called Solaris, IBM's is called AIX, Hewlett-Packards is called HP/UX, Apples OS X/Darwin is based on Unix, Linux (and its many distributions) is based on Unix, and then there are the various BSDs (OpenBSD, NetBSD, FreebSD).
These are considered the "flavors of Unix", and they are to some degree compatible to each other, or at least similar to each other.