Whatsapp have been growing over the last two years to the point that it has one of the biggest user platforms in the world. It does not necessarily means that it is the best messaging app ever created, but only that it gets the job done well enough for people to continue using it. However, it is a common misconception among Whatsapp users, that the first check mark means that the message has arrive to its destination and that a double check mark means the message has been read. After of a whole bunch of broken relationships, Whatsapp reveals its dirty secret:
- (Two checks) message successfully delivered to the phone of your chat partner.
Link: Whatsapp FAQ page