Plus Messenger is a non-official mod for the well-known messaging application developed by the same team that created the successful (though now extinct) WhatsApp Plus. The app is a modified version of Telegram that adds new features that were lacking in the official app.
The features that differentiate it from the original are many: the possibility of changing the interface color and theme, a new option that lets you share music with contacts, the possibility of hiding your phone number in group conversations as well as in individual chats, and an option not to show a notification each time a screenshot is taken in private chats.
The rest is exactly the same as in the original application, including every feature that makes Telegram a safe and robust instant messaging app.