where does 'pkg-config' takes its information from?

"http://linux.die.net/man/1/pkg-config

pkg-config retrieves information about
packages from special metadata files.
These files are named after the
package, with the extension .pc. By
default, pkg-config looks in the
directory prefix/lib/pkgconfig for
these files; it will also look in the
colon-separated (on Windows,
semicolon-separated) list of
directories specified by the
PKG_CONFIG_PATH environment variable."

"I found the info whilst poking around: I did

pkg-config --debug dbus-1

and I got:

/usr/lib/pkginfo
/usr/share/pkgconfig

a lot of times... so I guess I just need to drop '.pc.' files in those directories when I am building a .deb package."