The two main groups of image types are raster and vector. Raster images like JPEG, TIFF, GIF, BMP, and PNG are composed of pixels and can develop a “blocky” quality as the image is made larger because each pixel becomes larger. Vector images, like CGM and SVG, store lines instead of pixels. Using this method image size can be scaled without losing quality. The same vector image will appear correctly on a business card or a billboard.
Launch a .png file, or any other file on your PC, by double-clicking it. If your file associations are set up correctly, the application that's meant to open your .png file will open it. It's possible you may need to download or purchase the correct application. It's also possible that you have the correct application on your PC, but .png files aren't yet associated with it. In this case, when you try to open a .png file, you can tell Windows which application is the correct one for that file. From then on, opening a .png file will open the correct application.