This is from the book "Mothering the Mother" by Klaus, Kennell and Klaus. Its a wonderful book about how a doula can help you have a shorter, easier and healthier birth. Great reading!
Anyways, it says "Doula is a Greek word referring to an experienced woman who helps other women. The word has now come to mean a woman experienced in childbirth who provides continuous physical, emotional and informational support to the mother before, during and just after childbirth".
Doula isn't a new word. Women have been helping women in labor and in birth for thousands of years. Its only recently that pregnancy and childbirth was viewed as a medical condition and was taken out of the homes and into hospitals. I would again recommend that book and also "The Birth Partner" to help explain what a doula does or can do for you during your pregnancy, childbirth and post-partum.
Hope this helps~