Android 5.1 vs Android M - Permissions
One huge addition to Android M is permissions, and how each app handles and gets permission to use your device. This is rather advanced, but it basically gives users more control, peace of mind, and privacy with their devices and what apps can do on a device.
With Android 5.1 you see what permissions the app needs when you install it, as shown in our screenshot. With Android M the apps will have to ask permissions first. If something wants to access your camera, the user has to approve that permission. This means rogue apps can't access the internet without your approval first. Making Android safe, more secure, and protecting the users privacy on an app-by-app basis.
Users can even head into settings > apps > open an app and revoke permissions whenever they'd like.