I have a Samsung phone which is rooted and has xposed framework. There's an app "wanam exposed" it's runs using an xposed module. It can change themes of stock Samsung ROM. It can change color of notification bar, and almost anything. I want to ask that does it modify any configuration files? If so then what's the locationof those files? And all is changes can be reversed just by disabling the module in xposed app and restarting. How is that possible?
I've just published a blog article on that yesterday you might wish to read: Xposed: The mighty Android toolbox. Amongst others, it explains some background on how Xposed works.
Basically, the framework modifies the dalvik cache at boot time (or the corresponding art stuff on Android ≥ 5). So all changes take place on boot. Thus enabling/disabling modules only shows changes after rebooting the device: if you disable a module, it's changes simply won't be applied the next time you start your device.