Dizziness is a word that is often used to describe two different feelings. It is important to know exactly what you mean when you say "I feel dizzy," because it can help you and your doctor narrow down the list of possible problems.
Lightheadedness is a feeling that you are about to faint or "pass out." Although you may feel dizzy, you do not feel as though you or your surroundings are moving. Lightheadedness often goes away or improves when you lie down. If lightheadedness gets worse, it can lead to a feeling of almost fainting or a fainting spell (syncope). You may sometimes feel nauseated or vomit when you are lightheaded.
Vertigo is a feeling that you or your surroundings are moving when there is no actual movement. You may feel as though you are off balance, spinning, whirling, falling, or tilting. When you have severe vertigo, you may feel very nauseated or vomit. You may have trouble walking or standing, and you may lose your balance and fall.