sump pump versus grinder pump or both?

I've searched all over the net so am hoping to find an answer here. If one has a sealed grinder pump that's hooked up to the city sewer system, does one also need a sump pump or does the grinder pump perform that function also?

Thanks for any help in clearing up my confusion.

A sump pump is designed to remove ground water. A grinder pump reduces solid waste to a slurry and pumps it out. A solids pump moves solids and liquids (similar to a grinder, but needs a bigger outlet because there are still chunks).

You would also need a sump pump if you have the ground water issue. The grinder pump should be sealed for the waist water and having ground water flow into it would also let the shit water flow back into the ground.