Android 5.1 vs Android 6: App Tray
With Android 6.0 the application tray or drawer has been changed yet again. It's different on phones than it is on tablets, and you'll immediately see the changes in our screenshot. Instead of flipping through horizontal pages Google's gone back to one huge vertical scrolling list.
Apps are still listed alphabetically but there is now a dedicated row of the top four most recent launched apps on the top. This is for easy access to recently used apps, and the ones you use the most will start populating there more often as Android 6.0 learns from the user. There's also a search bar to easily search for an app. Start typing the name, and it will remove all icons and show relative apps for easy access and opening.
From the homescreen, a long press of the application tray button will instantly open the app tray, and the keyboard, for quick searching for whatever app you're looking for. Making opening apps easier and quicker. You can even search with your voice for better hands-free integration.