You have several options for mobile app development. Your choice depends on your aims. We recommend you determine the right audience and their specific needs. To ensure you target the correct audience, do some research before you start development.
Below are the main points on the options you can apply:
When you target a loyal audience that will pay for the app or will make in-app purchases, you should probably try iPhone development.
When you consider a corporate or an industrial app (e.g., an app for flights RocketRoute), you should think about an iPad version for your solution. Please note: iPad extension updates might require a separate app with a lot of code to be rewritten.
With an Android app, you can reach a wider audience and earn on ads. This type is popular for education, entertainment, and various utilities (e.g., fitness trackers).
Apart from native apps, there are web-based and hybrid apps suited for quick prototyping or for budget solutions as they target all mobile devices (and desktops too).
Also, apps can be developed via cross-platform frameworks that allow sharing an essential part of the code i.e., target both iOS and Android platforms with the same code. This way, Windows Phones can also run your app.