These links go to tutorials and explanations on how to edit photographs in post processing (after photographing them). These tutorials may be especially useful for "correcting" image colors and contrast/luminosity, sharpness and noise.

Various software, such as Adobe Lightroom Classic, Canon Digital Photo Professional, GIMP and several others, can be used to manipulate tone curves, but how it works is notoriously difficult to understand. Image editing tutorials may quickly help you to increase your understanding of various ways to edit images, compared to if you only play around and try learning everything yourself by trial and error.

People may edit images to make them more suitable for their purpose, compared to photos straight from the camera. Usually, more suitable means looking generally "better" and that they "pop", by changing them to become more pleasing to the human eye, drawing the viewers sight to the subject(s) in the photo, and/or subtlety/carefully tuning images to look more natural/realistic to the human eye. These tutorials may also be useful when editing digital images with various other purposes in mind.

If you intend to use your images in a photo competition, and/or share/display/publish the images at any place with rules/guidelines regarding image editing, make sure to comply. However, if you want to create image artworks for other reasons, you have much more freedom regarding image editing. Many photographers edit photos to remove/modify various distracting clutter/blemishes, "cleaning up the edges", and cropping/rotating the images to get more aestetically pleasing composition, and/or standardized compositons. Layering and stacking several images to refine the focus, and/or enhancing a special effect, and/or making composite/collage image that would be difficult/impossible to achieve with only a single exposure, can be very fun/interesting/useful. Edited and "doctored" photos have been around as long as the art and craft of photography itself.