Pixels Per Inch (PPI) is a measurement that indicates the density of pixels in a digital image or display. It tells you how many individual pixels are packed into one inch of space. 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 particularly important in devices like smartphones, tablets, and computer monitors, where image quality is crucial. For example, a display with 300 PPI will show finer details compared to one with 72 PPI, making it essential for tasks like graphic design and photography.