Are you asking what's a PDA? OR, what is a PDA?

PDA stands for Personal Digital Assitant. A PDA is a handheld computer, also known as palmtop computer, palm-sized computer, or pocket computer.

The first PDA is sometimes considered to be the Casio PF-3000 which was released in 1983. The Casio Boss and Apple Newton were early PDAs.

PDAs became very popular with the release of the Palm Pilot in 1996. Since then, PDA's have grown in popularity. These days, PDA's have merged with mobile phones. The BlackBerry, Treo, Pocket PC, and other smartphones can be considered PDA-phones.