Quasars may look like stars, but they are all very, very old and very far away. They are so far away it takes billions of years for the light from the quasar to get to us. There are no nearby quasars. And there are no young quasars. Quasars are several hundred billion times brighter than normal stars.
When radio telescopes were first used to examine the night sky, radio waves were discovered coming from distant point sources. Astronomers using regular visible-light telescopes turned toward these radio points and looked to see what was there. Some of the places where point sources of radio waves were found had no visible source other than a point of light that looked like a star. These objects were called "qausi-stellar radio sources", or "quasars" for short.
Later, it was found these sources must be very far away, far beyond our galaxy. Quasars are now considered the very bright centers of distant galaxies. The energy that creates the super bright light is probably due to the presence of a supermassive black hole at the center of that galaxy. Supermassive means it has a mass of about a billion of our suns. Astronomers believe that a quasar turns on when the black hole at the center of a galaxy feeds on gas and stars.
Image : NASA Chandra