Eclipse has a visual properties file tool for graphically composing you ant build.properties files. It makes reference to so-called "binary builds" as well as "source builds". The term source build makes sense: you're compiling sources.
"Binary builds" is throwing me off - is that referring to library (JAR) linking??
OK this one was a douzy - apparently Eclipse allows you to reverse compile your CLASS files back to Java files; this is also known as a "binary build" - you're literally building the bytecode back into source.