Krater comes from a word meaning "mix". Kraters were used for mixing wine with water. The Greeks thought it uncivilized to drink their wine neat, so these large bowls were used to mix wine with water.
Kraters were used at drinking parties called symposia, where men would talk and enjoy the company of male friends, whilst their wives were prevented from taking part. They were therefore symbols of a wealthy lifestyle. For this reason, they were sometimes used as grave markers for men and boys in early Greece.