An app must be permanently downloaded onto a device, most commonly a mobile phone, allowing the framework to be used even when offline. That being said, most app functionality requires being connected to the internet.
A mobile webpage is viewed in a browser – such as Chrome or Safari – and isn't stored on the device. Most of the same functionality and layout that an app would have can be built into this form of website. The functionality and layout of the original website can also be incorporated.
You can’t say that one is better than the other, as they are both useful in their own way.
To learn more about what can be done with a mobile webpage, check out two of our case studies below.