As explained in the article there are two main types of maglev.

The first is attractive where the train wraps around the track and magnets under the track pull the train up. Feedback control of the magnet current keeps the train from whacking into the track. The Shanghai train is of this sort.

The second type is repulsive. The train runs in a trough of conductive metal and magnets on the train induce a current in the trough that repels the train and it floats above the bottom of the trough. This is a result of Lenz's law of induced current. The train does not float when stopped, so it has to have wheels, but at 15 mph or so it takes off.

Both of these then need some way to move forward. A linear motor is used which is like a regular rotary motor that has been "unrolled". The track becomes the stator or the rotor of a conventional motor. This is why things get expensive fast. On the plus side they can handle 10% grades and acceleration is only limited by passenger comfort. They are most practical for comparatively short lines with multiple stops and high passenger loads.