Strong lensing is a phenomenon that occurs when a massive object, such as a galaxy or a galaxy cluster, bends and distorts the light from a background object, typically a more distant galaxy, creating multiple images or arcs of the background object. This effect is caused by the gravitational lensing of light by the mass of the intervening object. Strong lensing is a powerful tool for studying the properties of the lensing object, such as its mass distribution and dark matter content, as well as for magnifying and studying the background object in more detail than would otherwise be possible. It has been instrumental in studying the distribution of dark matter in galaxies and galaxy clusters, as well as in measuring the expansion rate of the universe and testing theories of gravity. Researchers use strong lensing to study a wide range of astrophysical phenomena, from individual galaxies to the large-scale structure of the universe. The study of strong lensing has the potential to provide valuable insights into the nature of dark matter, dark energy, and the evolution of galaxies and galaxy clusters.