Android is the name of the mobile operating system owned by American company; Google. It most commonly comes installed on a variety of smartphones and tablets from a host of manufacturers offering users access to Google’s own services like Search, YouTube, Maps, Gmail and more.
There is even a full application framework included, so third-party apps can be built and installed, then made available for the user to run as they like.
Android is an operating system for mobile phones and tablets, in much the same way that PCs run Microsoft Windows as their operating system.
Android is open source, meaning that manufacturers don't have to pay Google to use it, and that they're free to modify it. This means that it's used in a wide range of hardware varying in price from small budget phones to large-screen high-end handsets.