Linux is an operating system.......like Windows but without all the glitches that you can get with a microsoft operating system(just telling you what I was told about it)....and it is less memory hungy(if I have got this wrong I am sure someone on here will enlighten me).
Check this out Frank.
Linux.org | Resource for Linux | How to Linux guide | What is Linux
and this might help too.
Download | Ubuntu.
I had a laptop with Vista on it. I hated Vista with a passion and was going to download(Ubuntu) it to the laptop, but then I gave my laptop away(with a view to replacing it at some point)
You can run Ubuntu from a flash drive/memory stick if you want to try it first before doing the download onto your laptop.
Many netbooks run Linux operating systems and there are a couple of members on here who would not use a microsoft system if you paid them.
Hope this helps Frank.