Maglev (derived from magnetic levitation) is a system of train transportation that uses two sets of magnets, one set to repel and push the train up off the track as in levitation (hence Maglev, Magnetic-levitation), then another set to move the 'floating train' ahead at great speed taking advantage of the lack of friction. Within certain "medium range" locations (usually between 200-400 miles) Maglev can compete favorably with high speed rail and airplanes.
With Maglev technology, there are no moving parts. The train travels along a guideway of magnets which control the train's stability and speed. Maglev trains are therefore quieter and smoother than conventional trains, and have the potential for much higher speeds.
Maglev vehicles have set several speed records and Maglev trains can accelerate and decelerate much faster than conventional trains; the only practical limitation is the safety and comfort of the passengers.
The power needed for levitation is typically not a large percentage of the overall energy consumption of a high speed maglev system. Overcoming drag, which makes all land transport more energy intensive at higher speeds, takes up the most energy. Vactrain technology has been proposed as a means to overcome this limitation.
Maglev systems have been much more expensive to construct than conventional train systems, although the simpler construction of maglev vehicles makes them cheaper to manufacture and maintain. Despite over a century of research and development, maglev transport systems are in operation in just three countries (Japan, South Korea and China). The incremental benefits of maglev technology have often been hard to justify against cost and risk, especially where there is an existing or proposed conventional high speed train line with spare passenger carrying capacity, as in continental Europe, the UK and Japan.