One of the great things about Chromecast is the ability to show what is on your phone to a group. If you are giving a presentation on how to use the phone, it makes it possible for the group to see what you do in real time. Of course, by default, they won't be able to see exactly what and where you are touching the screen.
Fortunately, Android allows this to be shown in the developer options under settings. If you haven't enabled developer options, which is hidden by default, go to Settings and choose About Device. Tap on Build Number at least 7 times in quick succession. This will enable the developer options.
Within developer options, you can choose the "Show Touches" check box. Now, wherever you touch on the screen there will be a white dot. This will make giving group presentations about the benefits of using a smartphone much easier.