An LLM is stateless so every time you send a message a command is run with the parameters, the prompts, and a copy of the chat history when using one of those chat interfaces, and then it returns text. If the output includes explaining it to an LLM that would then be included in the copy of the chat history placed in the new command.

It would be a bit like opening a text editor and typing in that you want to increase the font size. Someone external to the text would have to come along and click the font options.

Yes but it implies it's doing its own "brain surgery" so if it got params wrong it could break itself. In that case you would have another AI behind the scenes doing the tweaking so it can understand you at a "subconscious" level.