The rectus abdominus is the name of the muscle that we commonly refer to as our abs. Most people develop their abs by preforming abdominal crunches. However, according to my Anatomy professor, you have to forcefully exhale while doing your crunches, because the rectus abdominus muscle has an important role in active respiration. Remember: in order to develop a muscle, you have to use the muscle in the way the muscle was intended to be used!
...and instead of working out to develop your "abs", you can just tape a six pack of rolls on your chest like this funny fellow did. Ha ha!