PPM (Portable Pixmap) is an image format developed by Jef Poskanzer. It contains human-readable text with an image header and body. Usually, the header includes the image contents such as the maximum color value, number of rows and columns, and the P3, which defines the image format. The image body, on the other hand, entails the actual picture data in a series of RGB values.
PNG (Portable Network Graphics) is a raster image file format released in 1996 as a replacement for JPEG. That said, PNG uses lossless compression that gives it a small file size while still maintaining the original image quality. Today, PNG format is widely used to share image graphics over the internet and is supported by programs like Paintshop Pro, Adobe Photoshop, Microsoft Paint, Apple’s Preview, etc.