Imagine that some person teleported from 2000 to these days. He meets some people and in order to be in contact with them he buys a mobile phone. He heard from them that they use messengers for communication that save money (you have no need to communicate through SMS anymore). So he opens the market and sees tens of different messengers: there are encrypted ones, blockchain based, simple, those that need no internet connection and so on. Which one to choose? It can be hard even for modern people. Usually we do our choice according to our friends and family choice. So what is your favorite messenger and why? I'm especially interested in private ones.