ARW (Sony Alpha Raw) is a raw, uncompressed image file format mostly used by Sony Alpha cameras. In this format, the data is saved using TIFF specifications. To open an ARW file, it, first of all, needs to be edited by a program such as Adobe Photoshop Elements.
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.