WhatsApp is a popular messaging platform originally designed for smartphones that allows various types of chatting and sending text, photo, audio or even video messages. It uses your phone's contact list to establish a connection between you and your contacts who also have your number on their phone. So when a contact installs WhatApp on his/her phone you can readily start communicating. For this reason even though the program is for a desktop PC you will need to first register the app on your smartphone. Other that that it is a very helpful app to message your contacts from the comfort of your PC.