Which os are u using?
All the macros used in the system are mentioned
in /usr/lib/rpm/macros file.
The macros are defined in various sections
of spec file......
In install section,to determine where the files
should be dropped when rpm is installed.
In File section,what files shold be included in rpm.
Like /usr/bin/ is mentioned by %_bindir
/usr/sbin/ is mentioned by %_sbindir