The document discusses how to generate image histograms using the Pillow library in Python. It explains that the histogram() method returns a list of pixel counts for each color band in an image. It provides an example of generating histograms for the red, green, and blue color channels of an RGB image, displaying the counts for each channel in separate figures. The code sample modifies two pixel colors in an image, gets the image histogram, and plots the histograms for each color channel.