Difference between content_main.xml and activity_main.xml?

Question

I am new to Android App development. I have Android Studio 1.4. In my layout folder I have two XML files (content_main.xml and activity_main.xml).

Answer 1

I think the content_main.xml is a part of activity_main.xml. Because there is include layout="@layout/content_main" in the activity_main.xml.