What is the extra pipe going into my sump pump pit?
You have two questions here,  First, I think the larger of the two pipes could be a vent pipe connected to a radon exhaust system.  Does this pipe connect to any other pipes or a box with  a radon sensor?

Second item, the receptacle shown is a single use type. Sump pumps will often nuisance-trip GFCI receptacles. Much the same as a refrigerator is put on a single non-GFCI receptacle to prevent nuisance tripping, a sump pump or other motor loads are also put on non-GFCI circuits. This is OK if the receptacle is a single use dedicated to the specific appliance.