now to me both are the same because a mobile is a phone but that's just me (because i still use my smart phone as exactly that, a phone). so i am wondering in terms of usage what is the difference between these 2 tags? if they are just the same thing then i would like to suggest aliasing one.
Those tags refer to different platforms with similar names. Windows Mobile is an old operating system series that had its last release in 2010 (the same year as the last use of the tag). This is a different thing from the modern Windows Phone operating systems or the upcoming Windows 10 Mobile operating system.