Google ART (Android Runtime)
aims to replace Dalvik and change the way your Android-powered smartphone runs. Dalvik is the one responsible for running apps on Android. Its runtime uses the JIT complier (Just-In-Time) to interpret bycode, which is a partial version of the original application code. ART uses the AOT process (Ahead-Of-Time) and basically pre-compiling the bycode into machine language the moment an app is installed, making them in essence native apps.
Source
http://www.gsmarena.com/google_debuts_art_in_kitkat_aims_to_change_android-news-7143.php
http://www.androidpolice.com/2013/11/06/meet-art-part-1-the-new-super-fast-android-runtime-google-has-been-working-on-in-secret-for-over-2-years-debuts-in-kitkat/
Saves much Battery. Saves More RAM. Running APPS Lessen like Bloatwares.
Just activate it by Developer Options> Runtime> Select " ART". Your phone will restart and will upgrade and optimize Applications installed. It will took 20 minutes or 10minutes Just make sure your battery is 70% at least or plug your charger.
If you can't find Developer Option, Go to Settings> Abput Phone> Tap " Build Number" 7times and you will unlock the Developer option menu. This is only Applicable to Kitkat OS.
PS. You can always go back to Dalvik Runtime ( Default runtime) by following steps above. Follow steps correctly and make sure phone has 70% battery above or plus a charger to avoid phone Bricking.
I'am not responsible if your device got bricked do this at your own risk. This is just to inform that you can enhance your Kitkat handset by running ART Runtime.
-- edited by monk12 on Oct 20 2014, 01:39 AM