The "build.properties" has the following entries:
# location of java library files (usually, you will have the beanshell, junit, database driver jars all in here)
# where to store temporary byproducts of the compile/test/package processes.
# examples: /tmp/robotracker, or ~/projects/robotracker/tmp
# where to put the release distribution
Ant reads this file so it knows where to find libraries, where to put temporary files, and where to put the final tarred gzipped package.