Lensing effects refer to the distortion of light from distant objects caused by the gravitational pull of massive objects, such as galaxies or galaxy clusters, along the line of sight. This phenomenon occurs due to the bending of light as it passes through the gravitational field of these objects, leading to magnification, distortion, and multiple images of the source object. Lensing effects can be used to study the distribution of dark matter in the universe, investigate the properties of distant galaxies, and test theories of gravity.