Channels appear in the apps, and are a good place to talk to other users on MeshCore.
You should be automatically subscribed to the #Public channel.

All hashtag channels are public, and visible to everyone.
To add any other hashtag channel in the official MeshCore app, it's easy to do. As one example, go to the Channels screen, and choose menu > add channel > join a hashtag channel > #test
If your software asks for a public key, then it's this:
izOH6cXN6mrJ5e26oRXNcg==
The #test channel, is great if you'd like to do tests of new equipment.
Specifically for "ping"/"pong" tests - use this channel to see if your signal is getting out, and if others can hear you. Most users will report to you how many hops it took to get to them. (Unlike Meshtastic, MeshCore has an upper limit of 63 hops, though we're unlikely to get that far!)
For emergency use.
Selling MeshCore related items? This might be for you.
The home on Meshtastic for mostly poor dad jokes
For weather information and reports
Expect motivational quotes and other famous sayings
We're unable to tell you what is in the #secret channel, because it's a secret.