Vertigo, known in the medical community as "benign positional vertigo," is a somewhat uncommon illness. It produces feelings of disorientation and problems with balance or identifying directions in the sufferer. Common, secondary symptoms include light to disabling dizziness; lightheadedness; vomiting; light to severe headaches; and it offsets the body's natural balance/equilibrium with its surrounding environment. (i.e., you fall down a lot, like Gerald Ford did.)
There are a multitude of causes for vertigo, though nothing really concrete has yet been established. Vertigo affects the bones in the inner ear that are responsible for the regulation of balance, motion and some gastrointestinal triggers in the body, which is why people with vertigo often vomit frequently. Generally, what happens is that your ear's balance system (which controls your whole body) gets stuck in one position, thus when you make a move in any direction other than the one that the balance system is stuck in, you become dizzy and nauseated.
In some cases, vertigo is accompanied by auditory hallucinations that occur only when your balance is thrown off, which really makes getting over it much more difficult due to the constant looking around for the source of the noise that the sufferer just heard. For me, it sounded like a bee buzzing around my head, only louder, from one ear to the other.
Vertigo is usually treated with motion sickness-controlling medicine such as Dramamine, or prescription-only drugs such as Meclizine (which is basically just a stronger version of Dramamine) and with having the sufferer's inner ear canals cleaned thoroughly by a doctor or qualified nurse practitioner.
Speaking from experience (I got vertigo as a part of SSRI cessation syndrome), vertigo is no fun. I highly recommend against contracting it.