I'm a little bit confused. So Linux Distro's aren't actually OS's?

They're just kernels? What is a kernel? and how do you define an OS?

What makes Mac osX and OS and Linux not?

Mac osX uses the darwin and mach. Those are kernels right?

I'd be very grateful if you could explain the differences.

Essentially, distro's are the Operating System (a kernel and a collection of pacakges). I guess I would define the kernel as the layer that interfaces between hardware and software.

http://en.wikipedia.org/wiki/Linux_distribution
http://en.wikipedia.org/wiki/Kernel_...ter_science%29

But Linux uses GNU? So Linux/Gnu is a full OS is it not?

Is fdisk from GNU? is ps from GNU? What is from GNU that is used in Linux.

Yes, many of the tools are GNU tools, which basically means they were developed under the GPL. GNU was supposed to develop it's own operating system based on a kernel called HURD. But linux took off and HURD has been dragging for years. I think finally the FSF has endorsed a distro, gNewSense, that contains totally free software.

http://en.wikipedia.org/wiki/GNU

Read this: Linux and the GNU Project

Think of the kernel as the smallest piece of SW that is required to have the computer do anything at all. (This is a bit imprecise, because you can take a stock kernel and remove all the unneeded drivers).

Then you add what some call utilities. Each is a program to take care of some specific function that is not built into the kernel. Example, the fdisk command.

The next layer is the application SW--eg OpenOffice--which the user can use to actually do something useful.

A Linux distribution--unlike Windows--typically includes all three. And, if you remove all the user applications, I think there are still more and better utilities than what Windows offers.

The Linux kernel came from Linus Torvalds (plus a community)

The utilities (and some applications) came from the GNU project.

An operating system is a kernel plus the minimum utilities needed to make it useful. Essentially, this is the Linux kernel, libc, gnutils (note that these can generally be replaced by, for example, busybox), and module tools.