The white arum is the 'original' plant and cv. Green Goddess is a cultivar which I presume arose in cultivation and which has been selected for its differences from the parent plant. Some cultivars breed true but apparently most do not. Both are weeds and will tolerate a wide range of habitat, including dry shade. In that situation they die back in summer. The central yellow bit is the flower and is mildly poisonous. (botanists please correct any errors!)