Definition of offline setting and online setting

Is there a document tell us about the concepts like offline, online here?
Is offline mean subspace is able to farm without network?

“NOTE 2: Following the commands above, you will be farming in an offline setting (by yourself). NOTE 3: To farm in online setting, you can modify the command accordingly.”

I’m not sure what you are talking about. Farming offline typically means for development purposes to test your changes, etc.

got it, thanks. By the way where could I find subspace design document helping to understand the code.

Maybe not as much about the code, but you should look at https://subnomicon.subspace.network/ first to understand what is being built in the first place.