Not able to understand debian-policy 8.1.1

[kamaraju kusumanchi <raju.mailinglists@gmail.com>]

In http://www.debian.org/doc/debian-policy/ch-sharedlibs.html , In 
section 8.1.1, in the second paragraph it says

The package must call |ldconfig| in the |postinst| script if the first 
argument is configure; ......... The package should call |ldconfig| in 
the |postrm| script if the first argument is remove. ............

first argument to what? a command or a file or a script? Which file is 
being referred to?

It is probably trivial once you know the answer. But I am confused as to 
what this paragraph is trying to say.

thanks in advance
raju

--
Kamaraju S Kusumanchi
Graduate Student, MAE
Cornell University
http://www.people.cornell.edu/pages/kk288/