The Portable Network Graphics (PNG) format was designed to replace the older and simpler GIF format and, to some extent, the much more complex TIFF format. (See the main page or news/history page for background information.) Here we'll concentrate on two major uses: the World Wide Web (WWW) and image-editing.
No detail was too small for consideration in the authors' quest for a near-perfect image format; yea, verily, even the acronym and pronunciation were major topics of discussion. The reason, of course, is the GIF format; some pronounce it with a soft G like giraffe, some with a hard G like gift, and no one really knows what they're talking about. (For the record, the soft G is correct; it is how the
author of the format pronounces it.)
"PNG" is always spelled "PNG" (or "Portable Network Graphics") and always pronounced "ping," not "pinj" or "pee en gee" or any other multi-syllabic disaster. See the introduction to the PNG specification for the definitive statement on the matter.