There are basically two types of mobile app development. The first is a per-determined features platform where the code has already been developed in-advance. Some my know it as a drag and drop platform. This platform has limitations to what you can do, but is a very cost effective way for developing a mobile app. Normally, this works great for non-profits and business apps.
Custom Mobile App
The second type of development is a custom coded mobile app. It is what it sounds like. You have an idea that no-one else has thought of, or you see a development and want to add your twist to it. This is where you present your idea on paper, create a wire-frame or email your notes. Having great documentation for your idea is one of the most important things needed when developing a custom mobile app.
Once you have all your documentation, the programmers takes the information and begin writing code to your specifications. The user Interface (UI) design work is normally done simultaneous. This can take anywhere from 30-120 days to complete. Depending on how complex the project is.
Note: My Pocket team can assist with developing a Wireframe for your project.