Dizziness or lightheadedness is the feeling that you might faint. Dizziness and vertigo have different symptoms. Dizziness is lightheadedness, while Vertigo is the sensation of spinning or moving, or that the world is spinning around you. Dizziness occurs when the brain is not getting enough blood to him, if there is a drop in blood pressure, if there is dehydration. The most serious diseases that may be associated with dizziness are arrhythmias, shock or heart attack.