The graphic design mockup is a composite image of how the final application screen will look. Color, layout, typography, and images are all worked out at this stage for each significantly different page type in the app. Please note, even though the composite (mockup or comp for short) looks like an app screen, it is still only a single image. It is not an app screen, and includes no code* at this point in the process.
*Note: I am not an engineer and will not provide any coding for my designs. My designs are intended to be handed off to a developer to produce your app for you using my designs as blueprints. I am available for design consulting at an additional hourly charge to ensure the engineer builds the app correctly.