Meditation is when you move your mind from a state of activity to a state of calm and silence, and then you are relaxed yet alert.
Meditation has been a practice of the major religions for years, this includes Ancient Hindu, Christianity, Jews and Muslims. These religious traditions may incorporate meditation but, of course, you don't need to be religious to meditate.
One of the traditions that include this practice is the philosophy of the Kabbalah. This focuses on meditation and prayer, teaching that these can enhance health and healing and also raise one's consciousness. The Kabbalah Center has 37 locations and a large collection of resources on their Web site: www.kabbalah.com.