There are a variety of different formats available for optical digital media storage today. There is the CD-ROM, HD-DVD, DVD-R's and HD-DVD-RW formats that are available. It can be a bit confusing, so you will want to know what the differences are between the different formats.
The specifications for digital optical media formats are set by working groups. These working groups are made up of various engineers that represent manufacturers that are planning to build and sell their hardware. Usually every manufacturer has their own technology developed as well that they want to include. When they make sure that the technology that is preferred is in their specification, every device that is sold earns them a royalty payment. Since these devices sell millions each year, the royalties paid can add up to a great deal of money.
Often there end up being format wars, since everyone wants to earn big money. One example of this is the format wars that occurred with BetaMax and VHD when the video cassette recorded emerged. Now days there is only one type of media that never had a format war, and that is the CD-ROM. Sony was able to hammer down most of the patents to the CD-ROM, which saved the format war problems from occurring.
The first format for recordable DVD's was called the DVD-R, which came about soon after DVD's first became popular. Many wanted to develop a way that the DVD's would have both read and write capabilities, which led to the development of two different formats. The two formats are the DVD+RW and DVD-RW. The difference between them is very small, and it actually is mainly the controller chip that is different, but in the end there is very little difference between them.
Eventually DVD-RW took a lead over the standard DVD-ROM drives; however, it is not a commanding lead. It was Phillips that was the first ever manufacturer to make a device that could read both of the RW formats for DVD, and they quickly became the standard device used.
Once again the format wars began. High Definition television requires a great deal more information that you can put onto a single DVD, so the high definition DVD drive and media format needed to be developed. These special devices actually use lasers with shorter wavelengths, which actually puts smaller dots on the recording media. There are two different formats, which are called BlueRay and HD-DVD, and they are just now beginning to enter the market. No one is sure which one will have better success, but more than likely a company that makes a device capable of reading both will win over the market. While HD-DVD's are cheaper, the BLueRays offer more storage space and also have a longer shelf life as well.
Usually it is the adult entertainment industry that picks out the winners in the market place. Currently they seem to be liking HD-DVDs for their formats of choice, and there are already people working on an HD-DVD-RW, and no doubt soon there will be another format war over this technology as well.