What is the Blue Tick on WhatsApp?

Well, you all must have observed a recent change in WhatsApp, that is seen on Android, iPhone, BlackBerry, Windows Phone, Nokia S40, Nokia S60 and BlackBerry 10. This is a new, a blue tick shown next to the messages that are already read by the recipient.

Well, until now WhatsApp just had the facility to show you whether the message is successfully sent and received by the recipient. But, like other messaging Apps like Facebook, it has now added on this extra feature to the app.
Here's something that is taken from the WhatsApp official Website.

Also, in a group, the blue checks will appear only if all the members in the group have read the message. That's like a lot of interesting stuff that WhatsApp has added!

But, for example there is just a single tick next to your message, don't simply assume that there is something wrong with the Mobile or WhatsApp. There are plenty of reasons why this might have happened?

• It might be that person is sleeping or the phone is off!
• There may be some network problems.
• They might have read the message when it flashed in the notifications but they might have not opened the app.
• They might have blocked you.

Now, here is an example for you:- 

Now, here the first message, is successfully send, received and read but the second message is successfully send and has been received by the recipient, but he hasn't read it.