The entire help system is kind of a kludge at this point, as it uses lynx to generate its output, using the HTML form of the documentation as input.
Basically, help is divided into several documents, listed in "help introduction is user's guide". The user's guide is one of those documents (you are reading a section of it, in fact).
Normally, you can just say "help string", but if there's a conflict you will need to specify which document to get the help information from.
Within any given help file, items after a number in square brackets are the names of other help entries (not the number in square brackets itself, but the words following it, generally terminated by a colon).