Due to the wealth of different ceramics created through the ages, the line between the two is often unclear in China, as the term (Ciqi) that means porcelain is used indisciminately for both china and pottery items, including those that are really a predecessor to real porcelain.
Here is a clear definition from a Chinese source to what should be considered Pottery and what Porcelain among Chinese ceramics.
Glazed Ming storage jar .
Needless to say that when speaking of porcelain the border between the two is often muddled by the fact that white clay was used in pottery like the Tang Sancai wares, and the clay of early Ming ceramics is often not white, but in China these often are called porcelain, especially those having a body covered by white glaze and with a blue decoration.
The above mentioned Tang Sancai or Sancai wares are low-fired and therefore according to the table below would fall in the pottery category. Some of the green/greenish glazed wares (Celadon) are also often called porcelain when they rather should be classified as glazed pottery.
Pottery
Porcelain
Material
normal clay
Kaolin (china clay)
Color
red, brown, gray
white
Firing temperature
600-800°
1200° or more
Properties
relatively porous& soft
non-porous, hard & strong
Tapping sound
dull sound
clear ring
Water absorbtion
high
very low or none
Body
non-transparent
semi-transparent
Characteristics
low chemical & mechanical resistance
high chemical & mechanical resistance
* This definition may differ in Europe due to the existence of "soft paste" porcelain, bone china and different clays.
Ceramic age separation in China Worth mentioning here is a separation of ceramics according to age, as used in China. Many collectors in China differentiate between so-called "ancient" ceramics, that is ceramics prior to the Song dynasty and "antique" or old ceramics (Song dynasty or later).
Experienced collectors often are specialized either on pre-Song ceramcis or those of the Song and later dynasties. The field of knowledge in Chinese ceramics is much too broad to allow for expert knowledge covering both. The actual time development of real porcelain is not quite clear but generally attributed to the Song dynasty, which is known for the first existing decorated porcelain.