Optical drives are any type of disk drive that uses light to store data. CD, DVD, and Blu-ray disks are all optical drives because they use a laser beam, which is a form of light, to read data off of a spinning disk. Optical disks are immune to magnetic fields that would destroy data on a hard drive or a floppy disk. Optical technology sold to consumers usually starts out read-only meaning that the consumer can initially buy a drive to read a disk, but cannot write to it. Later on, writable versions of the disks are developed for consumers.

In this discussion, "ROM" refers to a drive or a disk that is read-only, "R" refers to a disk that can be written to one time and never erased, and "RW" refers to a re-writable disk that can be erased and used again. 

CD-ROM drives were the first popular optical disk used in PCs. A CD-ROM drive can only read CD's. It cannot write and it cannot read newer technology such as DVD or Blu-ray disks. A CD-ROM drive can read mass-produced CDs, CD-Rs, or CD-RWs created by another computer. A CD holds 700MB of data or 80 minutes of uncompressed music.

CD-RW drives came after CD-ROM drives and allowed PC users to write their data or music to a blank CD. The blank CDs are called CD-R (write once) or CD-RW (re-writable). Like the CD-ROM drive described above, a CD-R/RW drive can read any kind of CD but not newer technologies like DVD or Blu-ray disks. CD-R/RW drives are often called CD burners because they use a laser to burn a dye layer in a blank CD.

DVD-ROM drives can read DVDs and CDs made in a factory or written in another computer. DVD-ROM drives cannot write. A DVD can contain up to two layers of data written on one side of a disk. Single layer disk contain 4.7 GB of data while dual layer disks contain 8.5 GB.

DVD-R/RW and DVD+R/RW drives add the ability to write to blank DVDs. They can also write to blank CDs. Due to fighting within the industry, there are two different standards for writable DVDs: -R/RW and +R/RW. Early DVD writers were either -R/RW or +R/RW and required the user to purchase the correct blank disks. However, once the disks were written, any DVD drive could read either. The confusion of "-" vs. "+" has largely been eliminated by drive makers selling drives that can accept either type of blank. DVD-R/RW and DVD+R/RW drives are often called DVD burners because they use a laser to burn a dye layer in a blank DVD. Early DVD burners could only write data in a single layer, limiting their capacity to 4.7 GB. Newer DVD burners can write to both layers (with the appropriate blank disks) for a total capacity of 8.5 GB. These drives are called "dual layer" DVD burners and have DL in their name and official logo.

Blu-ray, developed by Sony, is the successor to DVDs and hold 25 GB on a single layer or 50 GB on both layers. That gives Blu-ray disks enough storage capacity to hold high definition movies. Blu-ray burners are available for PCs and typically read and write all older formats listed above.

Below is a typical optical drive for a desktop PC. It is designed to be mounted inside the computer's case with only the front plastic trim piece visible from the outside. The IDE connector on the back plugs into the motherboard by a cable. The power connector receives a plug from the power supply. This drive happens to be a DVD±RW but all of the optical drives listed above look the same physically.