Wait so if I post in a channel, does everyone see it, or do they have to be in that channel to see it? Do “secret” channels exist?

It goes to all of your followers + followers of that channel (if you hit the algo threshold). So it's an additional boost.

No secret channels...yet

Ok thank u also what should I refer to u as when using this app, “your highness” or “my lord” or smth?

*furiously drafting an FIP with dynamic group key agreement cryptography*

You had the opportunity to do funniest thing.