During sleep, the brain remains very active, going through a number of well defined stages. In each stage sleep gets deeper as bodies gets more relaxed brainwave patterns slow down. A delta wave or delta rhythm is a large, slow brain wave associated with deep sleep.
Delta sleep is the most physically relaxed stage of sleep and is the time when the body recuperates and rebalances itself for the new day. Getting enough sleep, but more specifically enough Delta Sleep, is essential for healthy, productive living.