PPI, or Pixels Per Inch, is a measurement that indicates the density of pixels in a digital image or display. It tells you how many pixels are packed into one inch of the screen or image. A higher PPI means more pixels are present, resulting in sharper and clearer images, while a lower PPI can lead to a more pixelated appearance. PPI is an important factor in various devices, including smartphones, tablets, and computer monitors. For example, a display with 300 PPI will generally provide a better viewing experience than one with 150 PPI, especially for detailed graphics and text.