Resources
How CD Burners Work (Howstuffworks)
CDR-Info - The Recording Authority
DVDRHelp.com (formerly VCDHelp)
Glossary
Bootable CD - a CD that has the capability of starting the computer and providing some level of functionality. Normally a computer boots from a hard drive because the operating system is already there to boot from. How did it get there in the first place? One way is from a bootable CD that provides a way to start the computer and install the operating system, like Windows XP or Mac OS X.
CD Image - This is a file that is the entire contents of a CD in one file. It is commonly called an ISO image (in reference to an "ISO-9660 file system image"), but there are many other terms depending on the CD burning software. You can save an image file of the CD contents and burn an exact duplicate of the CD at a later time.
Data CD - Any CD with computer data that is read by a computer CD-ROM. Any type of file that can exist on a computer hard drive can be stored on a data CD.
DirectCD - This is a Roxio term for writing to a CD-RW as you would a floppy. It is also known as packet writing or Drive Letter Access (DLA), and a drive letter gets assigned (on a PC anyway) to the CD burner. You have less of a chance that any CD-ROM will read this disc because some drives (i.e. older drives) won't support this.
Disc-at-Once (DAO) - A method of burning a CD where the laser writes the entire disc without stopping. Good for audio CDs that don't have pauses between songs, such as live recordings. It also may be the only way to create a true duplicate of a commercial software CD that is copy protected.
DVD - Essentially a new format of CD, it contains over two hours of high quality video and audio, at a higher resolution than VHS tape or a video CD. Introduced in 1997, DVDs have begun to replace VHS video tape for the home video market. DVDs can also store data, almost 5GB (7x more than a CD), and DVD burners are available for less than $300. Data DVDs are read by computer DVD-ROM drives.
Music CD - Any CD that contains audio files and plays in a device other than a computer CD-ROM drive. This will include: a standard audio CD which will play in any home CD/DVD player, portable CD player, or car stereo CD player; an MP3 CD which play in many devices, but is not a universally supported format; a WMA CD which is gaining in popularity, but still behind the MP3 format.
Multisession disc - A disc that contains multiple sessions of data writing. For example, you have a 650 MB blank CD-R and you write 100 MB of data to it. That is session 1. You can then write another 50 MB, that's session 2. Then write 250 MB, that's session 3, and so on. You do this until you run out of space or write 99 sessions (also called tracks).
Photo CD - A Kodak product that contains photographic images that are scanned at several resolutions. A special player will read a Photo CD and display the images on a TV screen. This is the professional level product that provides images at resolutions up to 2048 x3072 pixels ( a "pro" version provides an even higher resolution). Hardware and software to produce Photo CDs is not at the consumer level. You request a Photo CD when you drop off your 35mm film to be processed, but generally only commercial photo developers offers this service. Multiple rolls of film can be placed on a single Photo CD.
Picture CD - Another Kodak product which is more consumer oriented that provides photos on CD at one resolution of 1024x1536. Again, you request a Picture CD when you drop off your film, but only one roll of film per CD. The CD also contains software to modify and enhance the digital images. Kiosks are provided in stores to print out pictures on Kodak paper.
Track-at-Once (TAO) - A method of burning a CD where the laser writes and then pauses after each track. With an audio it will leave a two-second gap between songs, which in some cases would be quite noticeable.
Video CD - A CD that can contains around 70 minutes of VHS quality video and audio, and plays in most standard DVD players. It uses MPEG-1 compression, the lower quality precursor to the MPEG-2 compression used in DVDs. Introduced in 1993, it never caught on in the U.S., but is very popular in Asia. It is also the CD type used in the creation of photo slide shows with music or narration.