What is an ejection pit and how does it differ from a sump pump?

A ejection pit and grinder pump receives raw sewage and gray water, stores in in the pit, grinds it up with a grinder pump and pumps it up to a overhead sewer main.
A sump pump sets in a pit and collects rain and ground water in the sump pit. When the water reaches a certain level a float switch turns the pump on and it pumps it outside or to a house drain. Hope this answers your question. Regards, Tom