Hybrid Apps are part native apps, part web apps.Like native apps, they live in an app store and can take advantage of the many device features available. Hybrid Apps is a Wep App that translate to Native code on a platform like iPhone or Androide. This Apps uses a browser view and hooks to allow your web to acess features on your mobile device like push notifications, contacts or data storage.
An hybrid app makes it easier to build multiple mobile apps for different platforms quickly.
Twitter ir an example of a hybrid app.