A Native App is an app developed essentially for one particular mobile device and is installed directly onto the device itself. Users of native apps usually download them via app stores online or the app marketplace, such as the Apple App Store, the Google Play store and so on. An example of a native app is the Camera+ app for Apple’s iOS devices.
A Web App, on the other hand, are basically Internet-enabled browser based apps that are accessible via the mobile device’s Web browser.
They need not be downloaded onto the user’s mobile device in order to be accessed. The Safari browser is a good example of a mobile Web app.