sump pump where does it empty to ?
Residentail sump pump discharge could go almost anywhere...piped into a drainage ditch, a "dry" sump pit, an underground perforated drain tile, a sewer or septic system, or just out on the surface of a yard, etc., unless there are some local code restrictions.
No telling. As long as whatever it is isn't plugged up and it takes all of the sump pump discharge with no problem, I wouldn't worry about it.
If that 4" pipe is "open", I would wrap it with something to prevent dirt, leaves, debris from eventually clogging it, however.