What is the difference between AppBarLayout vs Toolbar?
If you want just to include the Toolbar without any scrolling effects you can use Toolbar. But if you want to make some scrolling effects like on the images you need to use AppBarLayout.
The AppBarLayout is used to achieve various scrolling behaviors such as collapse, flex space, and quick return.
http://www.google.com/design/spec/patterns/scrolling-techniques.html
http://android-developers.blogspot.com/2015/05/android-design-support-library.html
AppBarLayout is a parent layout of ToolBar and ToolBar is custom ActionBar.if you want scroll action on the ToolBar so you should write ToolBar into the AppBarLayout,before you will write code for scroll the ToolBar, you must know the NestedScrollBar,it is used to scroll the ToolBar. but you cannot connect NestedScrollBar and ToolBar directly,because ToolBar is child of AppBarLayout and NestedScrollBar is sibling of AppBarLayout, that's why your Toolbar should in the AppBarlayout then you can connect AppBarlayout and NestedScrollBarLayout for scrolling action on the toolbar.