You can chat to friends that only have smart phones supporting this application and to friends having their account on Whatsapp. You can just send 100 messages in a month to friends not having Whatsapp on their phone.You must have access to internet to send and receive messages for free and the messages are also not sent to the phone inbox.You need to pay $0.99 for renewal after every year.You cannot call using this app to your friends for free.Your profile picture is visible to every person having your contact number and using this app, whether known by you or not.