The study examines the properties of 22,623 narrow-line AGN selected from a complete sample of 122,808 galaxies in the Sloan Digital Sky Survey. The research focuses on the [OIII] λ5007 emission line as a tracer of AGN activity. It finds that AGN of all luminosities reside almost exclusively in massive galaxies with distributions of sizes, stellar surface mass densities, and concentrations similar to those of ordinary early-type galaxies. Low-luminosity AGN hosts have stellar populations similar to normal early-types, while high-luminosity AGN hosts have much younger mean stellar ages. Young stars are not preferentially located near the nucleus but are spread over several kiloparsecs. A significant fraction of high-luminosity AGN have strong H δ absorption-line equivalent widths, indicating recent star formation. The study also examines the stellar populations of broad-line AGN and concludes that there is no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift. This establishes that a young stellar population is a general property of AGN with high [OIII] luminosities. The research highlights the importance of [OIII] luminosity in distinguishing AGN from star-forming galaxies and shows that AGN are found in massive galaxies with high surface mass densities and concentrations. The study also demonstrates that AGN hosts have similar structural properties to ordinary early-type galaxies, with no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift. The results indicate that AGN are located in massive galaxies with high surface mass densities and concentrations, and that their stellar populations are generally younger than those of normal galaxies. The study also shows that AGN hosts have similar surface mass densities and concentrations to ordinary early-type galaxies, and that the [OIII] luminosity is a key factor in distinguishing AGN from star-forming galaxies. The research provides important insights into the properties of AGN hosts and their relationship to the broader galaxy population.The study examines the properties of 22,623 narrow-line AGN selected from a complete sample of 122,808 galaxies in the Sloan Digital Sky Survey. The research focuses on the [OIII] λ5007 emission line as a tracer of AGN activity. It finds that AGN of all luminosities reside almost exclusively in massive galaxies with distributions of sizes, stellar surface mass densities, and concentrations similar to those of ordinary early-type galaxies. Low-luminosity AGN hosts have stellar populations similar to normal early-types, while high-luminosity AGN hosts have much younger mean stellar ages. Young stars are not preferentially located near the nucleus but are spread over several kiloparsecs. A significant fraction of high-luminosity AGN have strong H δ absorption-line equivalent widths, indicating recent star formation. The study also examines the stellar populations of broad-line AGN and concludes that there is no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift. This establishes that a young stellar population is a general property of AGN with high [OIII] luminosities. The research highlights the importance of [OIII] luminosity in distinguishing AGN from star-forming galaxies and shows that AGN are found in massive galaxies with high surface mass densities and concentrations. The study also demonstrates that AGN hosts have similar structural properties to ordinary early-type galaxies, with no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift. The results indicate that AGN are located in massive galaxies with high surface mass densities and concentrations, and that their stellar populations are generally younger than those of normal galaxies. The study also shows that AGN hosts have similar surface mass densities and concentrations to ordinary early-type galaxies, and that the [OIII] luminosity is a key factor in distinguishing AGN from star-forming galaxies. The research provides important insights into the properties of AGN hosts and their relationship to the broader galaxy population.