A good Linux guide for newbies?

I installed the latest Ubuntu on a second hard drive to play around. I have used linux in the past but for very specific things, like accessing a partition that Windows couldn’t read. So essentially I am a total Linux newbie.

I have several questions but some guides I found on the Internet are either way too technical while others just focus on the GUI.

For example, how can you install an application or driver? On Ubuntu it seems that the whole process is automated, you search for an app on the internet and install it. But where is the app installed and how can I do the whole process manually?

Also some drivers seem to be kernel-specific or distribution-specific. Why is that? Aren’t different distros compatible between them?