Hayd: the Hanafi range is three days and nights to ten days, with specific worship rulings.
Istihadah: bleeding outside the valid limits of hayd or nifas, not itself prohibiting prayer or fasting, though wudu rules may apply.
Nifas: bleeding after childbirth, with no set minimum and a Hanafi maximum of forty days.
Duration, established habit and timing of the bleeding determine the category.