Android 5.1 vs Android M - Google Photos
Google Photos isn't technically new only to Android M, and the new app is available now for those on Lollipop, but it's a completely brand new app that finally lets Android users manage photos unlike anything before.
You have unlimited Google Photos cloud storage, so you'll never lose a photo even if you lose a device. It automatically makes GIF, movies, slideshows, or vacation presentations with photos to share with friends and family, and much much more. Everyone is seperated by event, location or date, and a pinch will widen the view so you can see more (or less) photos at once. It's similar to Apple's photo app, but that's a good thing. Google Photos is an extremely powerful app we recommend everyone try today, so get it on the Google Play Store.