No lens is perfect, and some are a lot less perfect than others! All lenses display aberrations to some degree, including distortion, chromatic aberration (colour fringing) and vignetting (corner shading). These are worse with cheap kit lenses or zooms, and eliminating them optically is both difficult and expensive.

So it’s often more effective to put up with these slight optical imperfections in the original lens design and fix them digitally instead.

An increasing number of programs  now offer automatic lens corrections which can identify the lens used to take a shot and apply a specially-calibrated correction profile from that lens. The better the software, the better the corrections and the more lenses are supported.

DxO Optics Pro was the first in this field and probably still the best, though Lightroom’s lens corrections are really good too and Capture One Pro has profiles for a large number of consumer and professional lenses. These are probably the top three simply because they are RAW conversion tools you’d use at the start of your image-editing workflow anyway, but there are plenty of other programs which will fix your lens defects for you too.