  Strong gravitational lensing at the galaxy scale is a valuable tool for
various applications in astrophysics and cosmology. The primary uses of
galaxy-scale lensing are to study elliptical galaxies' mass structure and
evolution, constrain the stellar initial mass function, and measure
cosmological parameters. Since the discovery of the first galaxy-scale lens in
the 1980s, this field has made significant advancements in data quality and
modeling techniques. In this review, we describe the most common methods for
modeling lensing observables, especially imaging data, as they are the most
accessible and informative source of lensing observables. We then summarize the
primary findings from the literature on the astrophysical and cosmological
applications of galaxy-scale lenses. We also discuss the current limitations of
the data and methodologies and provide an outlook on the expected improvements
in both areas in the near future.
