PDA (Personal Digital Assistant) - definition
A handheld device with basic computing and organizing functions. Most of them have a large touch screen, a stylus and support handwriting recognition.
Normally, they also have faster processors than typical mobile phones and can run more complex software. Most of the PDAs run a standardized OS such as Windows Mobile for Pocket PC or Palm OS.
Today, PDAs are being pushed aside by capable smartphones, which can do all the same functions but also offer telephony.