What is dual layer dvd recording?

its a process like with one dvd files to another dvd.it copys da files to another disc. which we may call as writing from one DVD to another DVD

Dual-layer refers to the way the disc is "built". Dual-layer discs have two recording layers separated by a transparent spacer, unlike single-layer discs that have only one recording layer. The first layer of a dual-layer disc has a semi-transparent reflector layer that allows the laser to read and write to the first recording layer, but still lets the laser through to the second recording layer so that it can read and write to that layer also. Each recording layer has its own pre-groove, which controls the rotation speed and addressing for that layer. Additional dual-layer info: Typically, the rotation speed slows down when burning to the second layer of a dual-layer disc, so it is burned at a slower speed than the first. Dual-layer devices write the first layer from the inside edge to the outside edge of the disc, and the second layer from the outside edge to the inside edge of the disc. DVD+R DL discs are currently the only discs available for dual-layer writing. DVD+R DL discs are not rewriteable (cannot erase and rewrite to them). https://iomega-na-en.custhelp.com/cgi-bi...