The app drawer gets an overhaul in Android M. First off, it’s now a scrollable pane rather than a series of pages. Also, apps are grouped by which letter of the alphabet they start with, which makes it a little easier to find the app you’re looking for. These changes may be a bit jarring for long-time Android users, but they’ll make finding apps that much easier for everyone else.
http://www.greenbot.com/article/2939019/android/android-m-all-the-little-things.html#slide5