GetJar uses a customer loyalty program that rewards its users with virtual currency. This virtual currency can then be spent on in app purchases or premium apps in a wide variety of stores including the Google Play Store.
GetJar offers a mobile app for Android that is available on the Play Store, making for an easy way to install their store as well as start using the apps available on it.
The Android app is buggy where in there are issues with the in app currency as well as the store keeping track of purchases or applying themes to certain launchers.
For users that like browsing on their PC's GetJar might not be the best experience as it is only a mobile page. Browsing apps through this method is painfully unappealing.