What is the difference between a black hole and a quasar?
A black hole emits no light while quasars can emit light a trillion times brighter than that of our sun.
The exact nature of a quasar is unknown although they all seem to exist in close proximity to a black hole with the black hole providing large amounts of energy to the quasar.
All known quasars are in the billions of light years away. It can be speculated that quasars were an anomaly of the early universe because of their great distance from us, meaning there may not be any in existence right now but because of their great distance we can still detect them.