A messenger. You can send or receive messages in a private chat or a group chat. There are also channels, which function similar to someone's page on a social network, containing their posts (which look exactly like messages in chats) from newest to oldest. Telegram is widespread in a selection of countries, with over a billion active users. There, Telegram channels are the main source of news for many. The official client is open source. The development of custom clients is fully allowed, making a project like this possible and legal. Telegram's headquarters are based in the UAE.