Raw GPS provides satellite data directly to your device without processing. You will always see your location with latitude and longitude. You will also see altitude, speed and in what direction you are moving. All this data will be available to you whether you have Internet connection or not. You can save your positions to view them later in Maps and see where youve been. A tour outside the reach of any network can still be saved and viewed afterwards!
If you do have access to the Internet, you will also recive infomation about the place where you are, including country, city, zip code, street, etc. depending on what is available. It is also possible to mail or SMS-message your position from inside the app.
Pay attention to the "accuracy" that shows how good reception you have, the best value will be approximately 5 meter. To improve this ensure that the device has a clear view to the sky.