A fireplace is housing for an open fire inside a dwelling, used for heating and often for cooking. The first fireplaces developed when medieval houses and castles were equipped with chimneys to carry away smoke; experience soon showed that the rectangular form was superior, that a certain depth was most favourable, that a grate provided better draft, and that splayed sides increased reflection of heat. Early fireplaces were made of stone; later, brick became more widely used.

Source: Britannica