Pixel is the smallest single component of a digital image.
Internal surface of the monitor screen is coated with red, green and blue phosphor materials, that glows when struct by the stream of electrons. These colored cells are called dots.
Aspect Ratio (AR)
Aspect Ratio is the ratio of Number of X pixel (width) and Number of Y pixel (height). Standard aspect ratio = 4:3, 5:4 etc. Example: if resolution is 1024: 768 then aspect ration (AR) is 4:3.