Pocket PCs were PDAs (personal digital assistants) that ran Microsoft's Windows CE operating system. They were popular from the early-to-mid 2000s.
Pocket PCs were Microsoft's attempt to compete with Palm, which was doing extremely well in the late 90s. Microsoft had originally planned to call Pocket PCs Palm PCs, but Palm prevented this from happening. On April 19, 2020, Pocket PC 2000 was released.
Pocket PCs quickly became a major competitor to Palm's PDAs. They tended to be more feature-rich than Palm's offerings but were also a lot less simple and easy-to-use. Well-known brands such as HP, Compaq, Dell, Toshiba, and more all made Pocket PCs.
The Transition to Smartphones
Pocket PCs did very well for a while. However, by 2005, the need for a PDA had mostly disappeared. Smartphones, some of which ran Windows Mobile, could do all the things a PDA could and more. For this reason, the Pocket PC (as a PDA) had basically disappeared by the late 2000s.