WhatsApp is a texting service between mobile phones as a replacement for the regular SMS text messages. Over 900 million users are active worldwide using the Whatsapp service. Whatsapp uses an internet connection between phones. The service is available for iPhone, Blackberry, Android and Nokia Symbian60-phones.
The major difference between regular SMS text messages and Whatsapp text messages is that Whatsapp is free: You use the internet connection on your phone (wifi or part of you mobile data package depending on subscription or pre paid type).
SOURCE: HOW DOES WHATSAPP WORKS
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