So I know next to nothing about GPS and Apps, but I do want to get my feet wet and have a (simple-ish in my mind) idea for a simple app based on GPS or manual address.
I basically need to know if you can do something like this
if GPS Location is (11.111/22.222) { Show(**THIS STUFF**) }
or if manual address is (555 Main St, Salem, OR) { Show(**THIS STUFF**)}
in android or iphone
You can. It’s considerably more complex than that. And there are apps for both platforms that do exactly that. A quick search of Google, Apple Store, and Android Market will tell you what the current apps for that are.
If you want to do this yourself you will need to learn some new concepts. Geofencing (geographic buffers). Geolocation (address to coordinate conversion). And read up on how to efficiently use the location services provided by the devices you are writing for.