Pagers

The communication devices for messaging purposes are called pagers.
A pager is a small-sized (some are about the size of a business card) radio receiver capable of transfering information.

Wireless messaging is communicating through a pager when a phone call isn't appropriate or desirable, like when you're in a meeting, or if you don't want to be overheard.

With a 2-way text messaging service you can send, receive or reply messages to other pagers, to PCS phones or to anyone with an internet e-mail address.

It is a discrete way to exchange messages and send and receive Internet e-mail. You can also check headline news, music reviews, sports scores and more.

Most 2-way messaging devices have facilities such as storing and address book and more.

PDA Personal Digital Assistent, (handheld computer)
A Personal Digital Assistant, also called 'handheld', is a mobile device that is capable of storing, accessing and organizing data. Data such as phone numbers, addresses, schedules, notes and more. Most PDA devices can exchange this data with a computer (wired).