Sump and drainage pumps can be used for a wide variety of applications depending on the customers needs.
However most are to take away either sewage waste where the building does not suit a gravity fed sewer connection and below ground level water drainage.
The pump is connected to an outlet hose/ pipe at the top and is designed to be completely submerged. It then sucks up through the bottom and out at the top.
These systems will normally work on via a float or probe mechanism to control the levels. This allows the pump can be permanently left online and it will turn on/off automatically to drain down to a specific level.