LINE is one of the most popular apps in Japan, where I live. It is a communication tool that you can send a message to your family or friends. And you may call them by using it. There are, I think, 2 reasons why a large part of people in Japan have this very useful app. First, this app has very different functions for users. In addition to the examples I have shown- sending a chat and call your friends- , you are able to make an open chat, send a stamp like 😊🤩😱, and make it remind yourself to do something. Second, many people think that LINE is a very popular and common tool so that you may feel uncomfortable when your new friends want you to exchange LINE. For these reasons, a lot of Japanese people have this app.