PNG is a compressed LOSSLESS format.
Unlike GIF that is limited to only 256 paletted colours, PNG support true colour images with from 5 up to 16 bit per channels, including an optional alpha channel: 15 to 64 bit per pixel.
Electro, December 2013
PNG stands for Portable Network Graphic.
This format came about when there was a danger that useage of GIFs might be licenced. PNGs store the images without compression.
Mark Williams, September 2003
Hi L
There are several programs types which use the file extension .png including Paintshop Pro Catalogue files and Fireworks Image File. If you need any more information check out http://filext.com/detaillist.php?extdetail=png
That website can be used to look up information on all types of file extensions.