Earthenware and stoneware are both types of ceramics, but each is different enough to be be readily separated from the other. Primary differences are type of clay, firing temperature, glaze and, often, types of vessels made.
Earthenware is a porous ceramic fired at relatively low temperatures. Typically, it needs glazing to hold liquids.
Stoneware is fired at much higher temperatures, which allows the clay to become vitrified (glass-like), or nonporous. Stoneware is still usually glazed or slipped to increase its impermeability and for decoration.
Earthenware is kiln-fired twice, an initial "biscuit" firing at around 1,000 degrees Celsius and a second, glaze firing at around 1,100 degrees Celsius. Although the clay is less refined, stoneware is kiln-fired at 1,200 to 1,300 degrees Celsius to vitrify the clay.
Refined earthenware is usually glazed bright white with hand-painted, transfer-printed, or decaled decoration. Stoneware has a variety of glazes (and clay slips) such as salt-glaze, alkali, lead, Bristol and Albany, but stoneware decoration is more limited to painting or stenciling.
Refined earthenware is usually reserved for light-duty domestic objects such as serving dishes (plates, cups, saucers, etc.). Stoneware, with greater durability and impermeability, often is used for heavy-duty objects such as crocks, jugs and jars.