Aberrations, or optical imperfections, exist because no lens is optically perfect. Almost all lenses show aberrations from the ‘perfect’ image.
Almost all lenses suffer from aberrations, including distortion, chromatic aberration and vignetting. These are difficult to eliminate optically in the lens design, so software publishers are increasingly offering lens correction profiles to do this digitally. The software can identify the lens used from the image’s EXIF data and then find and apply the correct profile automatically.