The Android Runtime(Art): Java apps take too much memory and time to run inside the JVM especially running on low powered processors or low memory device.So in order to decrease these two factors Android have their own virtual machine to run the apps called the Android Runtime(Art). First .java code is converted to .class code. Then .class code is converted to .dex file. Finally the .dex file is converted .apk file. All .class, .dex, .apk are machine readable language. Android SDK: The Android Software Development Kit contains the libraries and tools you need to develop android apps. Some main things inside SDK: 1)SDK Platform: There's one for each version of Android. 2) SDK Tools: Tools for useful utilities like debugging and testing. 3) Sample Apps: To get information about how to use some APIs sample apps provide great help. 4)Documentation: Offline documentation. 5) Android Support: Extra APIs that aren't available in the standard platform. 6) Google Play Billing: It help...