Viber is one of the best ways to communicate with your friends. When you send a message to your fellow you get indication of your message status. You will get one grey tick when viber is sending your message. When you type your message and click on send button first you will see the grey tick on your screen. Then you will see two grey ticks that indicate your message has been read by recipient.
Open the viber
Click on contact with whom you want to start chat
By sending message you will see immediately after sending one grey tick will appear and then it will be turned in two showing that message is delivered to recipient.
In case recipient is offline you will see one grey tick as shown in image below
When your receiver will read that message then 2 grey ticks will appear along with message