True hard-paste, soft-paste, and reading a teabowl sherd.
Porcelain is white through the body, translucent where thin, and glassy-hard. Chinese hard-paste reached Europe by the shipload — blue-and-white export ware above all — and European factories imitated with soft-paste (slightly creamy, less glassy break) before mastering true porcelain in the 18th century.
On a sherd: check the foot ring (Chinese wares often show a neatly cut ring with tiny grit adhesions), glaze tone (Chinese glazes often faintly blue-green where pooled), and painting under versus over the glaze. Reign marks on Chinese bases are copied so routinely that a mark alone dates nothing.
Describe body, glaze, decoration, and translucency; photograph painted motifs and any base mark. Be candid that porcelain identification is connoisseurship — 'Chinese export, probably 18th century' with good photos invites the right correction if you're wrong.
Identifying pottery and ceramics
Identifying terracotta figurines