A level sensor is a device that measures the water level. This measurement provides feedback to a system, such as SCADA, controller or directly to the pump. Based on the information, the pump system starts up or stops.
There are pros and cons of the different systems. The main difference is the on-and-off measurement versus continuous reading of the level.
The Grundfos LC/LCD level controller is a water level sensor for municipal wastewater transport applications.