Android is a Linux-based operating system used primarily for smartphones and tablets. It has over 400,000 apps available and is open source software. Key features include messaging, graphics capabilities, a large app market, customization options, and visibility of information on the home screen. Android has gone through many versions since its initial 2008 release and now supports Java applications. The Android Market, later renamed the Google Play Store, allows users to browse and download third-party apps, of which there are over 400,000 available.