The PGM (Portable Graymap) image format is a plain text or binary representation used for grayscale images. Part of the Netpbm format family, PGM files store pixel values as intensity levels, providing a simple and efficient means to represent images with varying shades of gray. The format supports both ASCII and binary encodings, allowing for flexibility in terms of readability and file size. PGM files find applications in scenarios where grayscale information is essential and a lightweight, easily readable format is preferred.