«Levitation (from Latin levitas «lightness») is the process by which an object is suspended against gravity, in a stable position, without physical contact.
It is also a conjuring trick, appearingly raising a human being (or other object) without any physical aid. The illusion can be produced by clever mechanics, lighting arrangements and other means…»
For levitation on Earth, first, a force is required directed vertically upwards and equal to the gravitational force, second, for any small displacement of the levitating object, a returning force should appear to stabilize it. The stable levitation can be naturally achieved by, for example magnetic or aerodynamic forces. With the former, it is essential that diamagnetic elements are used. In this case the returning force appears from the interaction with the screening currents. For example, a superconducting sample, which can be considered either as a perfect diamagnet or an ideally hard superconductor, easily levitates an ambient external magnetic field. In very strong magnetic field, by means of diamagnetic levitation even small live animals have been levitated.
(taken from Wikipedia)