Final answer:
Holo, Material, and Holo .Light. Dark Action Bar are all names of Android themes used in different versions of the Android operating system to establish a coherent user interface design across applications.
Step-by-step explanation:
Holo, Material, and Holo.Light.DarkActionBar are all names of Android themes or style variations in the Android operating system. These themes were used to define the look and feel of applications on Android devices. Holo was introduced with Android 4.0 Ice Cream Sandwich as a way to create a more cohesive and updated user interface across Android devices. With Android 5.0 Lollipop, Material Design was introduced, bringing an even more modern and consistent design language with an emphasis on bold colors and motion.
Themes like Holo .Light. Dark Action Bar refer specifically to variations in the base Holo theme that, for example, change the color scheme and the presence of a dark action bar at the top of the screen. Developers used these themes to ensure their apps complied with the overall design language of the operating system and to provide users with a more seamless and predictable user experience when interacting with content loaded into their applications.