Portable Network Graphics is a compressed graphics format and is a bitmapped image format.
PNG was launched as a replacement to the GIF and is commonly used on the Web now. It is a popular choice to use graphics.
Different than the JPEG and GIF formats, the PNG format lets the alpha channel (or the RGBA color space) support 256-level of transparency. The main reason why the PNG format is used can be explained in that the PNG format eases the job of Web developers, graphic artists and icon designers by enabling them to place an image in front of a transparent background. Furthermore, most of the browsers and image editing programs accept PNGs.
However, PNG format is still not appropriate for all purposes;
PNGs occupy more disk space than JPEGs,
PNG images cannot be animated.
You can not only make one color transparent, but you can control the degree of transparency (this is also called "opacity").
Interlacing of the image is supported and is faster in developing than in the GIF format.
Gamma correction allows you to "tune" the image in terms of color brightness required by specific display manufacturers.
Images can be saved using true color as well as in the palette and gray-scale formats provided by the GIF.