Someone asked “why does "help(import)" not work?” I know the reason but it's not why I wanted to write about here. One reply exposed that I didn't know much about help. It shows a usage, that I had never known before:
help('import')

You can pass a string type, I also thought help is just printing out __doc__. And yes string also has __doc__, but why would you do that? Why would you want to get __doc__ of an instance of int, str, list, etc? So I never tried to pass a string to help.

Therefore I didn't known I could even get help about keywords. Moreover, I thought help was a function, which is not after I dug in. help is an instance of site._Helper. site module will be loaded automatically when you fire up Python interactive shell. Once it load, the help in shell is an instance of site._Helper.

If you invoke help without any arguments, help(), this will bring you to interactive help, I had never tried to use help without passing an object before.

This is actually invoking site._Helper.__call__, which is an instance method, means the instance of site._Helper is callable, and that's the way you get into interactive help.

site._Helper also has overridden __repr__ method, if you just type help and hit enter. The interactive shell will actually invoke this __repr__ method, and that's how we get this hint
Type help() for interactive help, or help(object) for help about object.

Note this does not directly mention that you can use help('string'), where string could be a module name, a keyword, or a topic. But you can know it from the message after you quit interactive help:
>>> help()

Welcome to Python 2.6!  This is the online help utility.

If this is your first time using Python, you should definitely check out
the tutorial on the Internet at http://docs.python.org/tutorial/.

Enter the name of any module, keyword, or topic to get help on writing
Python programs and using Python modules.  To quit this help utility and
return to the interpreter, just type "quit".

To get a list of available modules, keywords, or topics, type "modules",
"keywords", or "topics".  Each module also comes with a one-line summary
of what it does; to list the modules whose summaries contain a given word
such as "spam", type "modules spam".

help> quit

You are now leaving help and returning to the Python interpreter.
If you want to ask for help on a particular object directly from the
interpreter, you can type "help(object)".  Executing "help('string')"
has the same effect as typing a particular string at the help> prompt.

Maybe this is my excuse that I did know help better.