What is the difference between an App and a Program, NOTHING. Apps is an abbreviation for application, which is a piece of software. It can run on the Internet, on your computer, or on your phone or other electronic device. The word "app" is a more modern usage, but this is really the same thing as a program.
You can download iPhone apps from Apple App Store and Android apps from the Android Market.
Examples of Apps are Angry Birds, Boggle, Word, Excel