This paper presents a comprehensive study of the physical properties of ~10^5 galaxies with measurable star formation in the SDSS. By comparing physical information extracted from emission lines with continuum properties, the authors build a picture of the nature of star-forming galaxies at z < 0.2. They develop a method for aperture correction using resolved imaging, showing that their method removes essentially all aperture bias in star formation rate (SFR) estimates, allowing accurate total SFR estimates. They determine the SFR density to be 1.915±0.02 (rand.) ±0.42 (sys.) h_70 10^-2 M_sun/yr/Mpc^3 at z=0.1 (for a Kroupa IMF). The majority of star formation in the low redshift universe occurs in moderately massive galaxies (10^10-10^11 M_sun), typically in high surface brightness disk galaxies. About 15% of all star formation occurs in galaxies with signs of an active nucleus. About 20% occurs in starburst galaxies. The present to past-average SFR, the Scalo b-parameter, is almost constant over three orders of magnitude in mass, declining only at M* > 10^10 M_sun. The volume-averaged b parameter is 0.408±0.005 (rand.) ±0.090 (sys.) h_70^-1. This value is used to constrain the star formation history of the universe. For the concordance cosmology, the present day universe is forming stars at least 1/3 of its past average rate. For an exponentially declining cosmic star formation history, this corresponds to a time-scale of 7±0.7_-1.5 Gyr. The paper finds a correlation between b and morphological type, as well as a tight correlation between the 4000Å break (D4000) and b. They discuss how D4000 can be used to estimate b parameters for high redshift galaxies. The study uses the SDSS to analyze the physical properties of galaxies, including their SFR, stellar mass, and other parameters. The authors develop a method to model emission lines and determine physical properties of galaxies, including dust attenuation and metallicity. They find that the SFR density is higher in more massive galaxies and that the b parameter is a function of mass and metallicity. The study also addresses the impact of AGN activity on SFR estimates and the importance of aperture corrections in fiber surveys. The results show that the majority of star formation in the low redshift universe occurs in moderately massive galaxies, with significant contributions from AGN and starburst galaxies. The study provides a detailed analysis of the physical properties of star-forming galaxies and their evolution over time.This paper presents a comprehensive study of the physical properties of ~10^5 galaxies with measurable star formation in the SDSS. By comparing physical information extracted from emission lines with continuum properties, the authors build a picture of the nature of star-forming galaxies at z < 0.2. They develop a method for aperture correction using resolved imaging, showing that their method removes essentially all aperture bias in star formation rate (SFR) estimates, allowing accurate total SFR estimates. They determine the SFR density to be 1.915±0.02 (rand.) ±0.42 (sys.) h_70 10^-2 M_sun/yr/Mpc^3 at z=0.1 (for a Kroupa IMF). The majority of star formation in the low redshift universe occurs in moderately massive galaxies (10^10-10^11 M_sun), typically in high surface brightness disk galaxies. About 15% of all star formation occurs in galaxies with signs of an active nucleus. About 20% occurs in starburst galaxies. The present to past-average SFR, the Scalo b-parameter, is almost constant over three orders of magnitude in mass, declining only at M* > 10^10 M_sun. The volume-averaged b parameter is 0.408±0.005 (rand.) ±0.090 (sys.) h_70^-1. This value is used to constrain the star formation history of the universe. For the concordance cosmology, the present day universe is forming stars at least 1/3 of its past average rate. For an exponentially declining cosmic star formation history, this corresponds to a time-scale of 7±0.7_-1.5 Gyr. The paper finds a correlation between b and morphological type, as well as a tight correlation between the 4000Å break (D4000) and b. They discuss how D4000 can be used to estimate b parameters for high redshift galaxies. The study uses the SDSS to analyze the physical properties of galaxies, including their SFR, stellar mass, and other parameters. The authors develop a method to model emission lines and determine physical properties of galaxies, including dust attenuation and metallicity. They find that the SFR density is higher in more massive galaxies and that the b parameter is a function of mass and metallicity. The study also addresses the impact of AGN activity on SFR estimates and the importance of aperture corrections in fiber surveys. The results show that the majority of star formation in the low redshift universe occurs in moderately massive galaxies, with significant contributions from AGN and starburst galaxies. The study provides a detailed analysis of the physical properties of star-forming galaxies and their evolution over time.