Difference between PKG and DMG files.

Hello,

I'm coming from Windows and Mac file types seem really confusing, specially when you want to uninstall them.

As you all know, when you try to uninstall a software on Windows, it's never fully uninstalled because it's a mess, but at least I know where to go to when I want to uninstall something.

On Mac it's a whole different story. Sometimes I want to uninstall a file from launchpad, click and hold and I can see the X to uninstall it like an iPhone. Other times I don't see the X and have to go to the applications folder and delete it manually. I don't even know how to uninstall chrome properly.

And what's the difference between DMG and PKG files. Why PKG asks for my password as a way to authorize changes on the system and DMG does not. Which install format leaves more residue behind when uninstalling it? How do I remove the residue left after a program is uninstalled?

Thanks