How do you normally keep our sense of steadiness and balance?
Your brain constantly receives nerve messages from various parts of the body with regards to your bodily orientation and the orientation of your surroundings.
The three main sources of these nerve messages are:
-Your eyes - what you look at helps your brain to tell what position you are in and how you are moving.
-Nerve messages from your skin, muscles and joints help your brain to tell the positions of your arms, legs, and other parts of your body.
-Your inner ears. The inner ear includes the cochlea, vestibule and semicircular canals in which there is a system of narrow fluid filled channels called the labyrinth. The cochlea is the auditory portion of the inner ear. The three semicircular canals help to control balance and posture. As the head moves, the fluid in the labyrinth within the semicircular canals moves as well, and causes the movement of fine hairs that are on the inside lining of the labyrinth. When the hairs move, this triggers messages to be sent to the brain via a nerve called the vestibular nerve. This gives the brain information about the movement and position of your head, even when your eyes are closed. 
When being evaluated for dizziness, it is best to have all of these - eyes, nerve signals from the skin muscles and joints, and inner ears – check so that they are functioning normally.  
What are the causes of dizziness?
The following are the main causes of dizziness:  
Vertigo. Vertigo is dizziness with a spinning sensation. People with vertigo describe an unsteady feeling and a sensation that their surroundings are spinning around them, often accompanied by nausea. Vertigo tends to be eased by lying down flat, and made worse by sitting up or moving around. Vertigo is usually caused by a problem in one of the inner ears when the labyrinth or vestibular nerve is inflamed, damaged, or not working properly. If the labyrinth or vestibular nerve sends too many, too few, or wrong messages to the brain, and conflicts with other messages from the other ear, eyes, or body, the brain becomes confused and the result is vertigo. 
There are various inner ear problems that can cause vertigo. These include the following: 
Spinning. Many people can get vertigo for a short period of time if they spin around quickly, such as on a playground or on fairground rides. In this situation, the brain becomes bombarded with nerve messages from the semicircular canals in the inner ears due to the constantly changing position of the head. The symptoms usually subside soon after the spinning stops, but for some, the symptoms can last several hours or longer.  

Labyrinthitis. Labyrinthitis is inflammation of the labyrinth in the inner ear. The most common cause is a viral infection ('viral labyrinthitis'). Typically, the symptoms of viral labyrinthitis are vertigo, nausea, and mild hearing loss on the affected side. There may be other symptoms of a viral infection, such as a sore throat or headache.