Portable Network Graphic (PNG) is a relatively new image format used often on the web. It's similar to the JPEG format in that it allows images with many colours, but uses lossless compression so that there is no blurring or blocky edges. It is also similar to the GIF format in that it can be used to create very small and quick to download graphics using only a small colour palette. PNG also allows images to be transparent or partially transparent for smooth edges, but unlike GIF, does not support animation.
PNG is a patent-free format and is well supported by most web browsers and photo editing tools. Note: In versions of Internet Explorer older than 7, the transparency feature is not well supported.