What is the difference between Win CE and Win Mobile?
Ah, a great question...
A little over a decade ago, MS realized that computers aren't going to just be desktops anymore. The future of computing would be in embedded devices, like phones, store displays, car dashboards, stereos and music players, TV top-boxes, Video Game consoles, etc.
So, they created a "light" version of Windows based on NT that could be modular and adapted to anything from a store display to the Sega Saturn (the Saturn actually booted into CE for managing game data or browsing the web with IE). The idea was that someone could easily write code using a familiar Microsoft environment, and easily port it over to multiple types of devices without much effort. A great idea if you ask me, and waaaay ahead of its time (this was the 90s!).
They called it CE, which I guess means "Compact Edition", although they deny any official meaning behind it.
Windows Mobile is technically a version of CE. Its the version of CE that was adapted to mobile phones. That means software written for CE will technically work on Windows Mobile or Pocket PC, however it doesn't necessarily work vice-versa (if an app was designed especially for Windows Mobile, for example expecting a touchscreen or keyboard, it won't run properly on a sega Saturn that uses a controller to navigate).
Hope that wasn't too complicated.
I guess I could have just said "they're the same thing", but where's the fun in that (also not exactly the truth)!