The desktop app is a command line tool that you need to install, using npm. An in-depth guide on how to do this is located on the PhoneGap install page.
The mobile app removes the headache of code-signing and compiling. You can instantly view and test your work on your mobile device, saving you time.
Get the PhoneGap Developer App for the platforms you are developing on.
Using the desktop app, open a PhoneGap project and start a local server. Now grab your mobile device and enter the IP address of your desktop server. When the two are paired, magic will happen and you will see your app on the mobile device!
Now that you have paired your devices, as you change the source code the mobile app will instantly show your latest changes. With access to device APIs not available in web browsers, you don't have to sacrifice the confidence that your app will work as you intended on the devices you are targeting.