How do port Makefiles work

[Nerius Landys]

I'm trying to figure out how a port makefile configures, makes, makes
install from a source tarball.

The port I'm interested in in particular is /usr/ports/x11/Terminal; I have
it built and installed just fine using the ports system.  Now I'm trying to
tweak the source code, build, and install locally in a home directory, all
without using the ports system.  So, I've taken the archive
Terminal-0.2.6.tar.bz2, unpacked it, and ran './configure
--prefix=<PREFIXDIR>'.  Then I run 'make', and I get this error:

sylvester# make
make  all-recursive
Making all in doc
Making all in C
Making all in images
Making all in ja
Making all in images
Making all in helpers
make: don't know how to make balsa.desktop. Stop
*** Error code 1

Stop in /usr/home/nlandys/Terminal-0.2.6.
*** Error code 1

Stop in /usr/home/nlandys/Terminal-0.2.6.



But like I said earlier, the ports system was able to build and install
successfully.

So the ports build system is probably passing some arguments to 'configure',
and maybe some arguments to 'make', and maybe doing some other things and
calling other targets.  How can I figure out how the ports system is
building this package so that I can mimic it to successfully configure and
make this package manually?  Or, if that is not an elegant thing to do, how
can I correct this make problem?  In the end, I just want to build this
package manually.

Thanks
- A newb in need of help.