Terracottas are a clay like earthenware ceramic that can be either in glaze or not. In addition to be in use for flower pots, terracotta is also often in use for water and sewage pipes. It is in use for bricks, and sculptures as well.
The word “terracotta” comes from the Italian words for “baked earth.” Also, clay is the raw material, ceramic and pottery are generally the same thing. Just semantics, but some would disagree on definitions, porcelain is high fire, terracotta or earthenware is generally low fire. We can paint the products of terracotta for more decoration.