Earthenware is pottery which is porous (meaning water gets through tiny holes slowly). It was fired at a temperature which did not melt it into a glass-like vitreous form. So it is porous. Many types of pottery have been made from it. Until the 18th century it was the commonest type of pottery outside China.
Earthenware is a type of clay that when fired to make pottery is soft and can be scratched with a knife. It is opaque and has an grainy edge when broken. It is generally easier to shape on the potter's wheel than porcelain. Due to its porosity earthenware must be glazed in order to be watertight. Terracotta is earthenware.