I have a very basic question with respect to app development. I have no experience in app development, but, I need to reverse engineer android apps. When I reverse engineer (decompile using apktool or androguard) apps, I am seeing that every app has a package (folder structure) that begins with "com". Does every app have this com folder (I guess eclipse creates this folder, inside which the developers code). Is this assumption valid for all apps?
No, it's not. You can choose what to use as namespace. Many developers uses "com" for commercial applications and "org" for free ones but it's entirely up to you.