This format is used to create images without compression on Nikon Coolpix cameras. The created RAW files contain electronic data from the camera sensor. It is able to save more data compared with compressed photos. With NRW files you can set the exposure, white balance and other settings while preserving all the details in the image.
PNG is a raster graphic data storage format that uses lossless compression algorithm to Deflate. PNG was created as a free format to replace GIF. PNG supports three main types of raster images: grayscale image, a color indexed image and the color image. PNG format stores graphical information in a compressed form.