I believe that at the moment Viber and WhatsApp is a very popular messenger, it uses a huge number of people, except for usual correspondence it is possible to make paid calls to city and mobile phones, they can send text messages, sound signals, images, video, now 21 century and I'm sure it's safe!
Good time of day. Everyone has their opinion on this, but also have classmates, Vkontakte, there-there, Facebook, Twitter and many other applications that are no less popular, as well as you can make free calls, if you do not take into account the Internet, you can also conduct dialogues over a longer distance and many other chips. The best I think no, each application is unique in its own way, each has its drawbacks and its pros. In the 21st century, it became much easier to conduct dialogues and communicate with people at a greater distance thanks to these applications!