Not really getting how this bot works or how it's useful... What are its application?

User friendly, the Telegram base users is 60m so potential access to lots of people is pretty huge.
But I think the major use is Coinbase users can access their account through Telegram or a Getgems wallet.
I guess another step toward wider adoption.
Agreed. The 60 million user base of Telegram plus the users of Whatsapp is a huge audience for bitcoin. Even if 10% of those combined users, we will some dramatic surge upward, not only in price but also in adopters and users.

Back to the question, what does the bot do?
