Adjusting the levels is a non-destructive image editing technique because it does not permanently alter the pixel values of the image. This means that you can always revert to the original image if you are not satisfied with the results.

A histogram shows the distribution of pixel values in an image. This information can be used to adjust the brightness, contrast, and other tonal values of the image.

The Clone Stamp, Healing Brush, and Spot Healing Brush are all common types of retouching tools used to remove blemishes and unwanted objects from an image.

Layer masks can be used to create non-destructive edits, blend two images together, and add a drop shadow to an object.

Cropping, straightening, and rotating are all common techniques used to improve the composition of an image.

Color correction filters can be used to adjust the white balance of an image, remove color casts, and enhance the colors in an image.

The Median Filter, Gaussian Blur, and Bilateral Filter are all common types of noise reduction filters used in image editing.

Sharpening filters are used to make an image look more detailed by enhancing the edges of objects.

Adobe Photoshop, GIMP, and Paint.NET are all common types of image editing software.

Content-aware fills can be used to fill in missing areas of an image, remove unwanted objects from an image, and create a seamless transition between two images.

Photomontage, Double Exposure, and HDR Photography are all common types of image editing techniques used to create a surreal or artistic effect.

Vignettes can be used to draw attention to the center of an image, create a sense of depth, and add a dramatic effect to an image.

Cross Processing, Faded Effect, and Film Grain are all common types of image editing techniques used to create a vintage or retro effect.

Watermarks can be used to protect an image from unauthorized use, promote a brand or website, and add a personal touch to an image.

Desaturation, Grayscale Conversion, and Channel Mixer are all common types of image editing techniques used to create a black and white image.