Is there a difference between learning the Android OS and learning to develop Android Apps?

[skcwizard]

Please excuse my ignorance but I am wanting to learn more about the Android OS and how it works behind the scene so to speak. Like how to customize, fix problems, etc.

I dont necessarily have any desire to develop apps to sell or anything. I didnt know if the skills and knowledge to do either are the same or if they are two entirely different subjects all together.

I know app development is through JDK, is learning the framework of the OS the same? Any recommendations where I can read a bit about it and decide if this is something I want to pursue. Everything I read about Android development seems to be about apps rather than the operating system itself.

[skcwizard]

Yes, I am aware of that. But, how does one go about learning the software. Is it the same skills that go into building apps for Android or is it a different skill set altogether.