What is a crypto and Bitcoin telegram group?

Could you please elaborate on what a crypto and Bitcoin Telegram group is? I understand Telegram is a messaging platform, but how does it specifically relate to cryptocurrencies and Bitcoin? Are these groups typically used for discussions, trading advice, or something else entirely? Are they moderated, and if so, what kind of guidelines do they have in place to ensure a safe and informative environment? Lastly, how can one go about finding and joining a reputable crypto and Bitcoin Telegram group?