Porcelain and china are both "porcelain", what is the difference?

porcelain focuses on handicraft ceramics, and is more commonly used as a general term for "porcelain"

china focuses on non-industrial (e.g., everyday porcelain)

There are other terms such as ceramics, which is the academic term for "ceramics" and "silicate materials"

pottery is pottery, pottery making techniques, etc., and we often use this term to refer to pottery bars. This is the term we often use for pottery bars

stoneware is stoneware

clayware is clay