Source : Free On-Line Dictionary of Computing

Portable Network Graphics
     
         /ping/ (PNG) An extensible {file format} for the
        {lossless}, {portable}, well-compressed storage of {raster
        images}.  PNG provides a patent-free replacement for {GIF} and
        can also replace many common uses of {TIFF}.
        {Indexed-colour}, {greyscale} and {truecolour} images are
        supported, plus an optional {alpha channel}.  Sample depths
        range from 1 to 16 bits.
     
        PNG is designed for on-line viewing applications, such as the
        {World Wide Web}, so it is fully {streamable} with a
        {progressive display} option.  PNG is robust, providing both
        full file integrity checking and simple detection of common
        transmission errors.  Also, PNG can store {gamma correction}
        and {chromaticity} data for improved colour matching on
        heterogeneous {platforms}.
     
        {Filename extension}: .png.
     
        {RFC 2083}.  {W3C PNG pages
        (http://www.w3.org/Graphics/PNG/)}.  {PNG home page
        (http://www.wco.com/~png/)}.
     
        (1997-08-07)