When it comes to deciding whether to build a native app or a mobile website, the most appropriate choice really depends on your end goals. If you are developing an interactive game an app is probably going to be your best option. But if your goal is to offer mobile-friendly content to the widest possible audience then a mobile website is probably the way to go. In some cases, you may decide you need both a mobile website and a mobile app, but it’s pretty safe to say that it rarely makes sense to build an app without already having a mobile website in place.
Generally speaking, a mobile website should be considered your first step in developing a mobile web presence, whereas an app is useful for developing an application for a very specific purpose that cannot be effectively accomplished via a web browser.