Marshmallow brought a number of new shifts for Android users, but one of the biggest applause lines was given to the overhaul of app permissions. Before Marshmallow, you had only one way to deny an app a permission it asked for: don't install it. In Marshmallow, you can install an app and allow or deny permissions on a per-app basis. This means that if you don't think this game deserves access to your contacts list, you can deny it access to the contacts list.
And changing an app's approved permissions is really easy, but there is a small hurdle you may have to overcome.
Starting in Marshmallow, apps will ask for permissions as they go, meaning that when you try to place a voice call in Hangouts, it'll ask you for microphone permissions. When you ask to save or move a file, the app will ask you for Storage permissions. And so on. You can tap Allow, or you can tap Deny. Most users will likely hit Allow because the app is asking for a permission that is hopefully directly related to the action they are trying to accomplish.
However, mis-taps happen. Your phone slips, you were about to tap something in that area when the pop-up appeared in the same spot, things happen. If you didn't mean to make that choice, or change your mind about an app permission, here's where you can come to fix it. In Settings, we go to Applications. Select your app from the list, tap App Permissions, and you can turn on or off the permission in question.
If you're wanting to monitor apps across the board, you're in luck. There's a settings menu for that, too. Instead of tapping a single app in the Application list, we'll tap the menu button in the top corner and select Configure Apps and then App Permissions. You can now examine which apps have access to individual permissions. Decide you don't want any app to use your microphone? Well, tap Microphone and turn them all off.
Now, most developers are being highly encouraged to adopt the new permissions systems, but some apps are old or abandoned or haven't implemented it quite yet. When you try to turn off permissions in these apps, you get this warning. Older apps can indeed break when denied permissions that they need for certain functions, which is again why Google is encouraging devs to use them.
Now, keep in mind that denying apps permissions can indeed limit their functionality. If you turn off microphone access to your keyboard, don't be surprised when voice typing doesn't work. But if you didn't think that icon pack needed access to your text messages, you can shut that down.