AGN, short for Active Galactic Nucleus, is a term used to describe the central region of a galaxy where powerful energy emissions are produced. There are various synonyms for AGN including quasar, radio galaxy, blazar, and Seyfert galaxy. The term "quasar" is used to describe AGN that emit massive amounts of energy across the electromagnetic spectrum. A "radio galaxy" is visible via its radio waves, while a "blazar" is known for its intense jets of light. Seyfert galaxies are known for their active nuclei, with energy emissions being produced from a small region surrounding the galaxy's black hole. These synonyms are useful in understanding the diverse nature of AGN in the universe.