A PNG file is an image file stored in the Portable Network Graphic (PNG) format. It contains a bitmap of indexed colors and uses lossless compression, similar to a .GIF file but without copyright limitations. The file is commonly used to store graphics for web images.
The PNG format was created in response to limitations with the GIF format, primarily to increase color support and to provide an image format without a patent license. Additionally, while GIF images only support fully opaque or fully transparent pixels, PNG images may include an 8-bit transparency channel, which allows the image colors to fade from opaque to transparent.
PNG images cannot be animated like GIF images. However, the related .MNG format can be animated. PNG images do not provide CMYK color support because they are not intended for use with professional graphics. PNG images are now supported by most Web browsers.
NOTE: Mac OS X 10.4 and later saves screenshots as PNG files. Ubuntu Linux also stores print screen screenshots in the PNG format.