Broadly speaking, black stools are called black stools, and tarry stools are one of the types of black stools. Tarry stools are black, soft and shiny with mucus, resembling tar, and can smell like blood. Apart from tarry stools, taking iron, toner and herbal medicines can also cause black stools, which are lighter in colour, greyish-black and lustreless; consumption of animal blood products and liver can also turn stools black, but they do not have a bloody smell.