So I'm trying to move from windows/mac over to a linux based OS because I don't have the money to purchase proprietary software, and I'm trying to stay away from illegal downloading.

I've tried reading extensively about linux today, and I have a much better understanding then 24h ago.

My question is about distributions. My understanding is that there is, at the most basic level, a linux kernel, and what makes distro A different from distro B is just the software package that comes with the kernel. is that right? Is it possible to start with a very minimal linux distribution, and build it up (by installing software) to look like something fancy and versatile (like Ubuntu)?

Also, what does it mean when I read that a certain distribution is "using" debian or is a "version of ubuntu."

There's also something else I need advice/direction with. I just installed Ubuntu (it was really simple) and am actually using it to right this now. The thing is, even though I'm using a nice GUI, i'm not really learning anything about linux, or it's shell commands. The installation was too simple. Are there any distributions you can recommend that I can really learn from?