Pixels

Picture element is the actual terminology for the word, pixel, which helps to deliver a picture on a screen, or on a printed document. Depending on the type of document you want to produce, whether digitally or printed, the amount of pixels will change the image resolution to create a clear image.

For example 72 DPI (dots per inch) are preferably used for a digital image, as it is a low resolution, whereas if it was to be printed, it would have to be 300 DPI so that it is clear and the picture elements aren't visible from the image, due to it being a higher resolution.  Pixels also change due to the intensity of them, which is the brightness of the pixel, the intensity increases as the pixel is brightened and this will modify the contrast and determine the monochrome colours, as the pixel intensifies, more of the colour white is shown, and as it darkens, the colour black is more present.