Windows Phone (previously Windows Phone 7 Series) is a mobile operating system developed by Microsoft, and is the successor to its Windows Mobile platform. Unlike its predecessor, it is primarily aimed at the consumer market rather than the enterprise market. With Windows Phone, Microsoft offers a new user interface with its design language named Metro, integrates the operating system with third party and other Microsoft services, and controls the hardware it runs on.

Source: Wikipedia, "Windows Phone", available under the CC-BY-SA License.