Portable Network Graphic
/ˈpɔrtəbəl ˈnɛˌtwɜrk ˈgræfɪk/
An image format for use on the internet which has lossless compression and supports transparency.
PNG files use the same compression system that GIFs use, LZW compression, which differs from JPEGs whose quality deteriorates each time they are opened and saved. PNGs can therefore handle detailed documents with high contrast. Additionally, the format supports transparency: the ability to overlay PNG files onto different backgrounds. These qualities make PNGs the ideal format for screenshots and logos. However, PNGs are larger than JPEGs and don't support EXIF data.
Joint Photographic Experts Group (JPEG)