What is "emathia"

Emathia (Greek: ) was called the plain opposite Thermaikos Gulf when Kingdom of Macedon was formed. With this name was defined the area between the rivers Aliakmon and Loudias, which, because it was the center of the Kingdom was also called Macedonia. Emathia was one of the six earliest provinces of Kingdom of Macedon and was boarded on the west with Orestis, on the north was separated from Bisaltia by river Loudias and on the south was separated from Pieria by river Aliakmon.