The update will be available over-the-air (OTA) and will be pushed in batches, like all Android updates. Moving on, Android 5.1 is the first big maintenance release for Lollipop, fixing bugs and improving performance and stability over the original 5.0 release.
The quick settings panel has been polished up a bit in Android 5.1. Each of the icons comes to life with a new animation when you tap it.
Android 5.1 also introduces dual SIM support as a built-in Android feature. Android 5.1 brings some much-needed clarity to Lollipop's somewhat confusing screen pinning feature, which was designed to make it easier to lock kids or guest users into a particular app.
Device Protection in Android 5.1 will help to secure your device even if it's lost or stolen. With this feature enabled, a thief won't be able to use your device - even after factory resetting it - without having your Google account login details.
And some other minor changes are New animations in Clock app, Contacts lose colored overlay and Google+ linkage, Sticky soft keys fix, Hide 'Heads-up' notifications without dismissing, A new status bar icon when there's no SIM inserted, NuPlayer now the default streaming player.