What is menstrual blood, and when is a woman considered purified from it? Are there other types of menstrual blood that do not prevent prayer and fasting?

Menstrual blood is the blood that flows from a woman's uterus after she reaches puberty. It is often black with an unpleasant odor and is accompanied by pain. Its duration varies according to the woman's custom. Istihada (non-menstrual vaginal bleeding) is the discharge of blood outside the usual times of menstruation. It does not prevent one from praying, fasting, or engaging in sexual intercourse. A woman experiencing istihada is considered ritually pure. A woman recognizes the end of menstruation by complete dryness or by seeing the white discharge (al-qassah al-bayda').