you send a message to people from any other place in the world, and the message takes more time depending on the distance between you both (they can take from a few hours to a day and a half). You start by sending "public letters" that many people can read and decide weather to answer or not. I read a letter from a girl from germany (and the letter was in german), it was a long letter, I responded by talking about myself, saying that I'm trying to learn german and that it would be cool to exchange letters so I can practice the language, I also made some questions to continue the conversation. Mine was also a long letter. then she responded with a letter about 4 lines lenght IN ENGLISH basically saying "very cool, tell me more about you" wtf? and then something similar happened the same day in the same app, I say a lot of stuff about myself and ask some questions and the reply was "nice to meet you, tell me about yourself" this bothers me a lot, If you don't like my letter just don't answer.