Google Now is an app on your home screen that helps you get right information on right time. First of all the most important thing to notice is that this feature is available in Nexus and Google Play Edition devices with Android kitkat.
The Google Now launcher is officially exclusive to Nexus and Google Play Edition devices at this time. But if you want to install it in other devices, you can download the APK. Google Now Launcher supports the stock KitKat Launcher that comes with the Nexus 5. The ‘Apps’ and ‘Widgets’ tabs located at the top of the app drawer have been removed, instead the icons are enlarged.
Ok Google- When you are at home you can say Ok Google to trigger input through voice signal and then say loud and clear your queries. Other interesting features are faster search, large viewing area and intuitive wallpaper picker. This app has received an average rating of 4.7 out of 5 in Play Store.