Abstract
The author's current understanding of the nature and structure of active galactic nuclei is described, chiefly on the basis on optical spectroscopy, but including results of many authors, covering the entire observable wavelength of energy range. The importance of dust within the AGNs is emphasized, and current ideas of its distribution and of its effect on the observed spectra, are discussed. The torus model, polarization, and the "hidden Seyfert 1" nature of NGC 1068 and at least some other Seyfert 2 galaxies are discussed. It is likely that most QSOs, Seyfert galaxies and LINERs form one family, and there may be many as yet undetected low-luminosity AGNs in apparently normal galaxies. A working hypothesis, involving refueling of inactive galactic nuclei through galaxy interactions, is sketched.
