Windows Mobile is a family of mobile operating systems developed by Microsoft for smartphones and Pocket PCs.
Its origins dated back to Windows CE in 1996, though Windows Mobile itself first appeared in 2000 as PocketPC 2000. It was renamed “Windows Mobile” in 2003, at which point it came in several versions (similar to the desktop versions of Windows) and was aimed at business and enterprise consumers. By 2007, it was the most popular smartphone software in the U.S., but this popularity faded in the following years. In February 2010, facing competition from rival OSs including iOS and Android, Microsoft announced Windows Phone to supersede Windows Mobile. As a result, Windows Mobile has been deprecated. Windows Phone is incompatible with Windows Mobile devices and software.
The last version of Windows Mobile, released after the announcement of Windows Phone, was 6.5.5. After this, Microsoft ceased development on Windows Mobile, in order to concentrate on Windows Phone.
(Source – Wikipedia)