Learn in the textbookOptical Disc Storage Media — CD, DVD, Blu-ray
DefinitionA DVD is an optical disc that keeps the same 12cm diameter as a CD but raises recording density so that one side with one layer holds about 4.7GB.
ExplanationIt uses a red laser with a shorter wavelength than a CD's, making the recorded marks smaller and packing them closer, which gives it about seven times the capacity of a CD. A version with two recording layers holds about 8.5GB on one side. It became a common format for films and other video, and for storing large amounts of data.
AnalogyLike writing smaller and tighter with a fine pen so the same notebook holds more.
Memory hookDVD stands for Digital Versatile Disc, and true to "versatile" it carries both video and data.