This paper examines the properties of 22,623 narrow-line AGN selected from a complete sample of 122,808 galaxies in the Sloan Digital Sky Survey (SDSS). The study focuses on the luminosity of the [OIII]λ5007 emission line as a tracer of nuclear activity. The authors compare the properties of AGN hosts with those of normal galaxies, including stellar masses, sizes, surface densities, and stellar ages. They find that AGN of all luminosities reside almost exclusively in massive galaxies and have similar distributions of sizes, stellar surface mass densities, and concentrations to ordinary early-type galaxies. Low-luminosity AGN hosts have stellar populations similar to normal early-types, while high-luminosity AGN hosts have younger mean stellar ages. The young stars are spread over several kiloparsecs and not concentrated near the nucleus. A significant fraction of high-luminosity AGN have strong Hδ absorption-line equivalent widths, indicating recent star formation. The study also examines the stellar populations of broad-line AGN hosts and finds no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift, confirming that a young stellar population is a general property of high-[OIII] luminosity AGN.This paper examines the properties of 22,623 narrow-line AGN selected from a complete sample of 122,808 galaxies in the Sloan Digital Sky Survey (SDSS). The study focuses on the luminosity of the [OIII]λ5007 emission line as a tracer of nuclear activity. The authors compare the properties of AGN hosts with those of normal galaxies, including stellar masses, sizes, surface densities, and stellar ages. They find that AGN of all luminosities reside almost exclusively in massive galaxies and have similar distributions of sizes, stellar surface mass densities, and concentrations to ordinary early-type galaxies. Low-luminosity AGN hosts have stellar populations similar to normal early-types, while high-luminosity AGN hosts have younger mean stellar ages. The young stars are spread over several kiloparsecs and not concentrated near the nucleus. A significant fraction of high-luminosity AGN have strong Hδ absorption-line equivalent widths, indicating recent star formation. The study also examines the stellar populations of broad-line AGN hosts and finds no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift, confirming that a young stellar population is a general property of high-[OIII] luminosity AGN.