DVD-RAM: Is an optical disk that allows data to be read, written and erased. It's quite slow though. It can read all other formats such as CD-R, DVD-R. I think it can hold something like 2.6 gigabyte of information. Cheaper than DVD-R.DVD-R: Much faster than DVD-RAM. It works like "a big CD-R". Can hold 4.7 gigabyte of information. This is the format if you want to burn DVD-movies. Apples SuperDrive is DVD-R.