WhatsApp is a multiplat form application made as mobile phone messaging service for you to contact other WhatsApp users for free, that means it only uses your phone's internet connection to chat with and call other WhatsApp users.
If you wish to chat with your friends, you and that persona need to have WhatsApp installed on their phone, you will also need to add that person to your phone contacts so you can send him a message and start a chat.
Even though the main goal of this application is to send and receive messages, it also allows you to send images, videos and voice notes in a completely unlimited way. You can also pick a group of friends, create a group chat and have a group conversation and the best of all is that WhatsApp also allows you to have free phone calls with your friends.
Unlike the SMS, which are charged individually and they are not very cheap; the WhatsApp app uses the data plan of the cell phone or a connection via Wi - Fi to be able to send the messages free of charge.
So how this works? It is very easy, when the application is installed on your smartphone, this app uses the phone number as your user code, so the application get synchronize with your phone contact book and those who have the app installed and uses WhatsApp will immediately appear in the application so that they can be contacted by this means, This is a big advantage over other messaging applications because you do not have to add people individually to a separate schedule.
When you write a message through this platform it is sent to an HTTP server that is responsible for getting the message to the other person.