The title, MiniDisc (MD), comes from its size. Sony developed the MiniDisc in 1986 as an audio media that combines the merits of both CD (supreme quality) and Tape (recordable). The disc, with a diameter of 64 mm and thickness of only 1.2 mm, is placed inside a cartridge of 72 X 68 X 5 mm. The cartridge protects the disc from exposures like heat, liquids or anything else that might come in contact with the disc. It is built to withstand forces, like running or bumps in the roads, eliminating the problem of the disc "skipping." The MiniDisc also eliminates other problems such as scratches (CD), or tangles (tape). As a result, the disc does not deteriorate at the same rate, as do CDs and tapes.
Another advantage to MiniDiscs is that they are easily recordable. The process involves a laser head heating up the recording spot at the temperature of 180oC (400oF), while the recording head uses positive and negative magnetic signals to write audio data patterns. As the disc moves away, the magnetic recording head records new spots while the already recorded spots cool down retaining the magnetic signals. All these complicated processes require no physical contact between the laser/recording heads and the disc itself. This is why Sony claims its MiniDisc can be recorded up to one million times before failure.
The MiniDisc's popularity has increased rapidly for many reasons. The first is its size. The MD can fit in about any pocket and is extremely lightweight. There are models for home, portable and home use on the market. With the mp3 technology increasing, many brands have made USB connectors and even software to attach the MiniDisc "portable recordable" unit up to the computer. Other uses for Minidiscs that are being explored include digital cameras and video recording.
More information can be found at the minidisc web site.