Preview of version: 7 (current)
Windows CE is the name of the core operating system that Windows Mobile devices use.
Also, Windows CE was the name of the original PDAs that were released in 1996. It looked like a version of Windows 95 running on a smaller screen. However desktop Windows applications do not run on these devices.
The first devices were called the Handheld PC. They used MIPS and SH3 CPUs and had as little as 2 MB of ram as well as a 4MB of rom.
The second family of devices were called the Palm-size PC. They also used MIPS and SH3 CPUs and had as little as 4MB of ram and 8 MB of rom. The Palm-size PC resemble the next generation called Pocket PC. Originally the devices were called Palm PCs however Palm sued for copyright infringement and the name was changed to Palm-size PCs.
The versions are documented at http://www.pocketpcfaq.com/version.htm
Plus! Pack for Windows CE Handheld PC Pro Edition Version 3.0
Windows Media Player 1.2 for Handheld PC (MIPS4, SH3, ARM)
Pocket PC Talk News