The term mobile app is like the term science. Science has such a broad meaning that it begs countless questions if someone simply refers to himself or herself as a scientist. What kind of scientist? Are you a rocket scientist with SpaceX? Are you with the Cancer Research Institute? Maybe you're a botanical scientist studying the environment. The list is endless. Many think the definition of a mobile app just refers to games like Candy Crush that litter common platforms like Apple iTunes or Android Apps on Google Play. But just like science, mobile app has a much more extensive meaning.
The broad definition of a mobile app, short for mobile application software, is that it is application software (as opposed to system software) specifically intended to run on mobile devices like tablets and smartphones (as opposed to apps designed specifically for desktop computers). The Google Play app store lists over 20 mobile app categories, and the Apple App Store has 24. The point is that mobile apps run the gamut from games to productivity apps to health and fitness apps. Just like there are all kinds of different scientists, there are all kinds of different mobile apps.