Is it true that linux is not an OS but just the kernel? the actual OS is GNU which is powered by the linux kernel..
Thanks in advance for the clarfication
If you are going to be picky, indeed, Linux is the core, the kernel itself.
It gets generalised into the whole platform, but you could go as far as calling those 'Distributions'.
Some history: http://www.gnu.org/gnu/linux-and-gnu.html
If one wants to be really picky, then yes, Linux is just the kernel and not an OS. "Linux" only indicates that it's "a Linux system" (ie. using the Linux kernel) and not that it's "the Linux system", as there is no such thing.
Linux is an OS as windows, it is only a miss concept.