It's not a group, it's a channel. The difference (for the most part) is that in a group there is discussion, all members can talk. A channel is a "group" that only admins can speak in, and all members can see. (Think of it as a tv channel)
I don't know about reaching more people, as most people that have telegram have other forms of social media as well, but taking myself as an example, I actually don't have Facebook, rarely check twitter, and spend a lot of time on telegram. So it's very convenient for me.
First picture is a group of just a few people (
who sent their links and this guy send it to his ad channels free of charge and the second one is just a guy who has a big channel and I asked him to put dansdeals on his broadcasts! Hopefully this helps spread the message and increases followers.