Magnetic levitation, maglev, or magnetic suspension  is a method by which an object is suspended  with no support other than magnetic fields. Magnetic pressure is used to counteract the effects of the gravitational and any other accelerations.
Earnshaw's theorem proves that using only static ferromagnetism it is impossible to stably levitate against gravity, but servomechanisms, the use of diamagnetic materials, superconduction, or systems involving eddy currents permit this to occur.
In some cases the lifting force is provided by magnetic levitation, but there is a mechanical support bearing little load that provides stability. This is termed pseudo-levitation.

Magnetic levitation is used for maglev trains, magnetic bearings and for product display purposes.
Data from  http://en.wikipedia.org/wiki/Magnetic_levitation