This workshop has repeatedly stressed the utility of observations in previously underused spectral regions, particularly the ultraviolet and X-rays, for understanding the physical nature of low-ionization nuclear emission-line regions (LINERs; Heckman 1980b). Nevertheless, the amount of data on LINERs available from space-based instruments is still very small, limited by a combination of the long exposure times necessary to detect the faint signal in these sources and the usual oversubscription of spacecraft time. Thus, statistical studies of LINERs, which require large quantities of data to be gathered in ``survey'' mode, still must rely on more traditional ground-based capabilities. This contribution reviews the current status of optical spectroscopic observations of LINERs. Using a recently completed survey of nearby galaxies, I will summarize the demographics of LINERs in the context of other emission-line nuclei. Next, a number of statistical properties of LINERs will be compared with those of low-luminosity Seyfert nuclei, with the hope that such a comparison may shed some light on the parameters of the host galaxy nuclei that influence the various manifestations of nuclear activity. Many of the properties of these faint nuclei are being scrutinized for the first time, and some interesting trends, not obvious or otherwise overlooked in older surveys, will be noted. Finally, I address the fraction of LINERs that show evidence of broad-line emission akin to that seen in Seyfert 1 nuclei and QSOs; this subset of LINERs provides strong support for the hypothesis that a large fraction of all LINERs truly share the same physical origin as other classes of active galactic nuclei (AGNs).
Excellent reviews covering some aspects of the topics presented here, but based on older work, have been given by Keel (1985), Heckman (1987), and Filippenko (1989, 1993). It should be emphasized at the outset that the material presented here refers exclusively to compact LINERs (r 200 pc) found in the central region of galaxies, and not to LINER-like nebulosities sometimes observed in other environments (see Filippenko in these proceedings for an overview of these systems).