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I review progress made in understanding the nature of the broad-line region(BLR) of active galactic nuclei (AGNs) and the role BLRs play in the AGNphenomenon. The high equivalent widths of the lines imply a high BLR coveringfactor, and the absence of clear evidence for absorption by the BLR means thatthe BLR has a flattened distribution and that we always view it near pole-on.The BLR gas is strongly self-shielding near the equatorial plane.Velocity-resolved reverberation mapping has long strongly excluded significantoutflow of the BLR and shows instead that the predominant motions are Keplerianwith large turbulence and a significant net inflow. The rotation and turbulenceare consistent with the inferred geometry. The blueshifting of high-ionizationlines is a consequence of scattering off inflowing material rather than theresult of an outflowing wind. The rate of inflow of the BLR is sufficient toprovide the accretion rate needed to power the AGN. Because the motions of theBLR are gravitationally dominated, and the BLR structure is very similar inmost AGNs, consistent black hole masses can be determined. The good correlationbetween these estimates and masses predicted from the bulge luminosities ofhost galaxies provides strong support for the similarity of AGN continuumshapes and the correctness of the BLR picture presented. It is concluded thatalthough many mysteries remain about the details of how AGNs work, a generaloverall picture of the torus and BLR is becoming clear.

What broad emission lines tell us about how active galactic nuclei work