For many years it was found that no quasars could be identified beyond a redshift of 2.0 or so, then in the 1980's this barrier fell as new search strategies were used, and now the most distant known quasars are at redshifts near 4.0. This corresponds to a time when the universe was only a few billion years old. Quasars, then, provide us a snapshot of what the universe was like when it was very young, and many more quasars existed compared to today. What a quasar is, in and of itself, is a difficult question because, like cancer, there may be several different mechanisms that give rise to this phenomenon. Astronomers still believe that not all galaxies went through such a phase when they were young.
Quasars are also weird for at least one other reason.
Careful radio observations show that the location of the energy produced by some if not all quasars is in a region only a few light years across. Since there is no way you can stuff 100 Milky Ways into a region of space this small, this has called for exotic proposals for energy production. These SBHs have a mass equal to over a billion times the mass of the Sun. When dust, gas and stars fall into these holes, their material gets temporarily parked in an orbiting 'accretion disk' kind of like the rings of Saturn. Friction within this disk then causes mater to flow into the black hole and give up nearly 50 percent of its rest mass energy.