DVD stands for Digital Versatile or Video Disc, DVDR stands for DVD Recordable and DVDRW for DVD ReWriteable. A single layer* DVDR(W) fits about 2 hours of very good quality DVD-Video, MPEG2, including several audio tracks, stereo, Dolby Digital or DTS and also advanced menu systems and subtitles. If you choose to lower the video quality it is possible to store several hours video on a DVDR(W) using low bitrate and low resolution with quality more like SVCD,CVD. It is also possible to have ordinary data on a DVD that can be played by all DVD-ROMs.
Today does it exist some different types of DVD Recording standards, all those only support single layer DVDrs(DVD-5)* which mean that you can store up to 4.7 BB (4.37 GB)* data or up to 2 hours of very good video. The formats are:
DVD-R and DVD-RW
DVD-R is none rewriteable format and is compatible with many existing DVD-ROM drives and many DVD-Video players(very roughly about 85% of all players).
DVD-RW is a rewriteable format and it is compatible with many newer DVD-ROM drives and DVD-Video players(very roughly about 65% of all players).
These formats are supported by DVDForum.
DVD+R and DVD+RW
DVD+R(W) has some better features than DVD-R(W) such as both CAV and CLV writing.
DVD+R is a none rewritable format and is compatible with many existing DVD-ROM drives and many DVD-Video players(very roughly about 80% of all players).
DVD+RW is a rewritable format and is compatible with many newer DVD-ROM drives and many DVD-Video players(very roughly about 70% of all players).
These format are supported by the DVD+RW Alliance.
DVD-RAM
is not compatible with most DVD-ROM drives and DVD-Video players. Think of it as a removable hard disk that can also read DVD-ROM discs. This format is supported by DVDForum.
Currently there are many writeable and rewriteable formats on the market and it can be confusing to the general consumer. These formats include:
DVD-RAM
DVD-R
DVD-RW
DVD+R
DVD+RW
DVD-RAM
DVD-RAM is a format primarily used as a data solution, although the type of data stored can include many types of data including video. Early version 1 recorders used 2.6 GB discs (or double-sided 5.2 GB discs), but current version 2 drives can handle 4.7 GB discs (or double-sided 9.4 GB discs). These discs are traditionally housed within a cartridge which cannot be opened, so that the media is well-protected. Newer Type 2 cartridges can be opened however, which is important for some people who wish to read these discs in drives or standalone DVD-Video players/recorders which do not use the DVD-RAM cartridge loading mechanism.
DVD-RAM is a sanctioned format of the DVD Forum, a consortium of companies involved in the development of DVD standards. DVD-RAM is a very robust data storage solution, theoretically allowing greater than 100000 rewrites per disc. In addition, similar to a hard drive, it allows full random read/write access and has defect management. An additional benefit of DVD-RAM is that, having been around for several years, it is a tried and true technology which has native support in Windows XP and Mac OS X. The discs are usually formatted with the UDF format, but can be formatted to such formats as FAT32 in Windows and HFS+ for Mac, or others. The main drawback of DVD-RAM is its very limited read compatibility in DVD-ROM drives and standalone DVD-Video players. DVD-RAM read support in these machines is increasing however.
DVD-R and DVD-RW
DVD-R and DVD-RW are both also supported formats of the DVD Forum. Both formats generally use 4.7 GB discs (generally without cartridges), although some DVD-R drives used 3.95 GB discs.
DVD-R is a write-once recordable format which allows excellent compatibility with both standalone DVD-video players and DVD-ROM drives. There are two main types of 4.7 GB DVD-R discs: DVD-R for General Use and DVD-R for Authoring. Most consumer drives use the former cheaper General Use discs, while many higher end professional drives use Authoring discs. The correct media type appropriate for the drive must be used when burning. However, once burned, the discs should be able to be read in either drive type. (General Use DVD-Rs are designed to prevent backup of encrypted commercial DVDs.)
DVD-RW uses rewritable discs which are rated at more than 1000 rewrites in ideal situations. Unfortunately, DVD-RW does not enjoy the same excellent compatibility with DVD-ROM drives and standalone DVD-Video players that DVD-R enjoys. Another drawback is that unlike DVD-RAM, one must generally erase a DVD-RW disc before reuse.
Most DVD-RW drives should also be able to record to DVD-R. However, the reverse is not true. Many older and some current DVD-R drives are not capable of writing to DVD-RW discs (but may be able to read burned DVD-RW discs). Some drives can also record to CD-R and CD-RW.
Currently DVD-RW and DVD-R have heavy penetration into the multimedia market as well as the general consumer market. For instance the Apple SuperDrive, found in higher end Mac computers used in multimedia creation, is simply a DVD-R/DVD-RW (and CD-R/CD-RW) capable drive.
DVD+R and DVD+RW
These two formats are backed by the DVD+RW Alliance. While these formats are not sanctioned by the DVD Forum, several members of the DVD+RW Alliance are also members of the DVD Forum.
DVD+RW, like DVD-RW, is a rewriteable 4.7 GB DVD format. DVD+RW, however, in some ways offers some technical advantages, which for example include: lossless linking (which in turn more readily allows editing of a disc's contents after an initial write while maintaining integrity of the remaining data), currently slightly faster recording speeds, and optional future Mount Rainier drag-and-drop file access support (also known as DVD+MRW). However, DVD+RW does not have the very high compatibility with standalone DVD-video players and DVD-ROM drives that the DVD-R format enjoys. The level of compatibility of DVD+RW is said to be similar to that of DVD-RW. Also, DVD+RW does not currently have the same level of market penetration as DVD-R.
DVD+R is a format that only was introduced to the public very recently (early 2002). DVD+R is a write-once 4.7 GB format which promises to dramatically increase the compatibility with standalone DVD-Video players and DVD-ROM drives. Whether that claim is fulfilled remains to be seen, but initial reports have been very positive. It must be noted, however, that 1st generation DVD+RW drives do not support DVD+R burning, and it is likely that most cannot be upgraded to do so either. If one wishes to have DVD+R burning functionality, one must purchase a newer drive specifically designed to do so. DVD+R discs currently are somewhat more expensive than DVD-R discs, but prices will likely drop with time.
Can't I have it all?
Unfortunately, no. While combinations DVD-RAM and DVD-R/DVD-RW do exist, currently there are no drives capable of burning to both DVD+R/DVD+RW and DVD-R/DVD-RW discs.
So what should I buy then?
This is a very difficult question. The choice largely depends on one's usage environment and usage preferences. DVD-RAM offers very good support for data applications and is used in many professional environments, but the discs cannot be used in most DVD-Video players and DVD-ROM drives, making it less attractive for the average home user. A few newer DVD-Video players and recorders do support DVD-RAM however.
DVD-RW/DVD-R has the highest market penetration and DVD-R offers the best proven support for video playback in standalone DVD-Video players. Not only is it very well supported for PC users, it is the format of choice for the Mac.
DVD+RW/DVD+R is beginning to gain market share, and the data capabilities of DVD+RW do offer some advantage to DVD-RW. DVD+R compatibility with DVD-Video players is as yet (April 2002) not proven to be as high as DVD-R, but initial reports have been very favourable and suggest a significantly higher level of compatibility when compared to DVD+RW and DVD-RW.
From - http://www.cdrom-guide.com/forums/showthread.php?t=164572