Characters have emotions. Typography plays a crucial role in determining the emotional connection that your product makes with your user. It is one of the most important or maybe even the most important aspect of UX. Determining the type and font for your product again starts with understanding your user and the nature of your product.
Typography is a world in itself and there are huge number of resources available online if you feel like indulging. As a designer do not play it safe and experiment to get the type that expresses your product best and that your user can relate to.