Select a channel name above; it is only visible to its participants, and used as the encryption key for every message. Nobody can read messages without it.
At most 10 timestamped encrypted messages are kept on the server. No IP or identifiable information, not even the nickname, are kept in clear.
Anybody can wipe channels whenever they'd like. Server restarts wipe everything as history is only in-memory.
You do not have to trust me and can run your own instance if you prefer. Sources.