Blank media DVDs are available in many different formats.
DVD-R, for DVD-Recordable (sometimes spoken as DVD minus R) is a writing format for the storage of data according to DVD specifications so as to be playable on any compliant DVD player. DVD-R media can only be written to once, up to 4.7GBs worth of data. Two versions of DVD-R blank media exist: one for professional content developers used to make master discs that serve as models to be mass-produced by postproduction facilities, and the more common one commercially available for general use.
DVD+R (usually spoken as DVD plus R) is another recordable format which stores data according to official DVD specifications for playback on compliant DVD players. The + simply refers to the method used to follow disc tracks: - uses Constant Linear Velocity (CLV) for disc rotation, while + can use CLV or Constant Angular Velocity (CAV), which allows for easier data access. DVD+R also provides for lossless linking of new data added by multiple recording sessions.
DVD-RAM, for Random Access Memory, is a rewritable format, meaning data can be recorded and erased up to a hundred thousand times. DVD-RAM blank media utilize phase-change data layers and can function as virtual hard disks.
DVD-RW (DVD minus RW) stands for DVD-ReWritable, and is similar to DVD-RAM except that it uses a sequential read-write method more akin to a phonograph than a hard disk. It can also only be rewritten to about a thousand times.
DVD+RW (DVD plus RW) is very similar to DVD-RW, but uses a different technique to track the laser around the disc while writing data. DVD-RWs use CLV while DVD+RWs can use either CLV or CAV for disc rotation, with CAV providing easier access to the data. DVD+RW media also allows for lossless linking of new data inserted by multiple recording sessions.
BD-R refers to Blu-ray Disc Recordable media that can be written to only once using the Blu-ray Disc standard, allowing 25GB of capacity for single-layer discs and 50GB of capacity on dual-layer discs.
BD-RE media are discs that can be written to using Blu-ray Disc specifications many times. Available in capacities of 25GB and 50GB for the standard 12cm disc, the latest versions can be found in a smaller 8cm size for use with camcorders.