Kaolin is a clay which be used in white-ware ceramics fabrication. Sometimes, it's called China-clay because it was first used in China.
We can distinguish all 3 words from firing temperature, hardness and porosity. Porosity inverse variation with firing temperature. Porcelain is the lowest porosity of 3 types, next is Stoneware and earthenware, respectively. Earthenware is the highest porosity and leaky, usually used in planting ceramics.