PNG pronounced ping is a format for storing bitmapped (raster) images on computers. It was created originally to replace the GIF file format when it was announced that the companies who created the GIF format wanted royalties. PNG uses indexed colors and lossless compression (like a .GIF file), but without those copyright limitations; it cannot be animated like a GIF image.
PNG images are in many ways better than .GIF as they also include an 8-bit transparency channel, which allows the colors in the image to fade from opaque to transparent; GIF images only support fully opaque or fully transparent pixels. PNG supports palettes of 24-bit RGB colors, RGB images or greyscale or RGB images. PNG was intended to be able to transfer images on the Internet, not professional graphics, and so does not support other colour spaces (such as CMYK).
Apple Preview Corel Paint Shop Pro GIMP - The GNU Image Manipulation Program (LINUX) Microsoft Windows Photo Gallery Viewer Safari
Developed in 1982 by Adobe Systems, the .ps extension is a file type used by the publishing industry. Prior to the development of PostScript, it was not possible to print images and text on the same page. Postscript addressed this by defining a language that allowed applications to instruct the printer how to display objects on the page. This file type revolutionised publishing allowing certain curved items to be printed that previously could only be printed on specialist CAD printers. Although no longer as popular or common as it was historically, it is still an important file type.
PostScript is actually a programming language as well as a file type. Typically files are created by applications such as Adobe Acrobat or Quark Xpress. Now a legacy file format, most printers and programs continue to support this format, with the only pre-requisite being a printer utility that supports PostScript. The file basically contains a set of instructions that tell the printer what to print and provide the co-ordinates on the page of where an object or text should be printed.