What Are channels?
And also: how do they work?
Channels are a way to organize your messages and conversations, but offer no additional functionality (that's not already part of scuttlebutt).
Subscribing to a channel will let you read messages from your friends (and friends of friends) who have written in this channel. You will not, however, see any channel messages from folks not in your network. You do not need to subscribe to a channel to see a message a friend posts to it. You will see it on your main feed simply cos they're a friend and you're interested, on a technical(and emotional!) level, in what they have to say.
An analogy! If scuttlebutt works as a big diary--with each message you post added to the end of your diary and shared with your friends-- then channels are like writing a diary entry with a different colored pen. They are simply a pleasing, personal form of organization. But luckily your friends follow this same technique and use the same pens and so you can easily share your related messages.
There has been discussion on whether channels should work more like hashtags, and to have a distinct "group" feature that would behave closer to a slack channel or discussion group. You can read more of that conversation here
- Answer compiled from multiple posts on this thread Shoutouts to @kas, @dinosaur, and @dominic for the help!