There are two basic types of blank CD's - Writable (CD-R) and Rewritable (CD-RW).
CD-R's are considered "write-once", meaning that once data is written it cannot be erased. However, you can write to a CD-R many times using the multi-session option in your burning application (Roxio and Nero both support it) until the disc is full.
CD-RW's can be written to and erased many times (up to 1000 times supposively). You work with them same way you would work with CD-R's. However, there is one additional feature available on CD-RW discs. It's called "packet-writing" which utilizes the UDF format. Programs like Roxio's DirectCD or Nero's InCD format the CD-RW, which can then be written to or erased on the fly much like a floppy disk.
The clear advantage of CD-RW is the ability to erase, with the added option of packet-writing. However, CD-R's are cheaper and more compatible across music CD players. Most CD players, for example, won't be able to read CD-RW discs. Optical drives on computers can read them, however.
There are several types of blank DVD media: DVD+R, DVD+R DL, DVD+RW, DVD-R, DVD-R DL, and DVD-RW
Visit the site below to learn more about each of the different types: http://www.videohelp.com/dvd
Dual-Layer (also called "Double-Layer" or DVD-9) refers to blank DVD media that can hold up to 8.5 GB of data. Standard DVD+R or DVD-R (also called DVD-5) can only hold up to 4.7 GB. A standard 4.7 GB is enough space to accommodate roughly 2 hours of true DVD-quality video (even less for extremely high-quality MPEG-2 video). In order to hold more, you would have to compress the video to make it fit, which of course causes a loss in overall quality. Also keep in mind that authoring a DVD with menus and extra features takes up additional space. Dual-layer discs provide almost double the space and are compatible on all modern DVD players. DVD burners have become pretty standard in new computers and are capable of burning in both the + and - R/RW formats.
As for making DVD's, there are two basic types: DVD-video and data DVD's (I'm not getting into audio here). The site I linked to above has quite a few tutorials on how to make DVD-video, along with links to some free tools. For data DVD's, you pretty much use the same kind of software you would use for CD-R's and CD-RW's.
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