Ok. I am in learning mode again folks. Sorry in advance! What is the difference in these formats? I assume They must have some differences since they sell them seperately. My Imac will use them all but for what specifically? Optical Media CD-R CD-RW DVD-R DVD-R for Authoring DVD-RW DVD+R DVD+RW DVD-RAM Blu-ray & HD DVD Optical Media + this and - that! another language!