True air suspension uses air bags to support the weight of the car. It is nice in that it can change the ride height of the car on the fly, so it is also is utilized as a helper system in the rear of some cars to assist the regular suspension under heavy loads to keep the car level. Electronic suspension comes in two forms. The first is the older design, which has solenoids that changed the size of the piston orfice inside the shock/strut to provide a firmer or softer ride depending on a signal from a computer. The problem with this design is that it is slow to react (relatively speaking) and relies on too many moving parts that are not servicable. The new style changes the viscosity of the fluid in the strut, instead of the size the fluid must pass through. It accomplishes this with a special fluid that increases in viscosity in proportion to the amount of magnetism applied. This uses no moving parts (outside of a regular strut) and is extremely quick to respond to changes in the road surface.