Android is an open source software platform and operating system for mobile devices based on the Linux kernel. It has seen several updates since its original release, including Cupcake, Donut, Eclair, and others. Android allows developers to publish applications to the Android Market without approval, unlike Apple's App Store which requires a month-long approval process. The Android SDK includes development tools like an emulator, plugins for the Eclipse IDE, and DDMS for debugging applications in the Android runtime environment.