2.  JPEG is a standardized image compression mechanism.  JPEG stands for Joint Photographic Experts Group.  JPEG is designed for compressing either full- colUor or gray-scale digital images of "natural", real-world scenes.  It does not work very well on non-realistic images, such as cartoons or line drawings.

3. PDF stands for Portable Document Format. PDF was introduced in 1990 as a way to reliably view, print, and share information with other people. PDF is a proprietary format that allows you to read electronic documents, either on or off line. This format provides a page-by-page view of documents, exactly as they appear in their printed form, as well as allowing keyword search.

4.  PNG stands for Portable Network Graphics. its a file image that contains a bitmap of indexed colours under a lossless compression.  commonly used to store graphics for web images.  The PNG format was created in response to limitations with the GIF format, primarily to increase colour support and to provide an image format without a patent license.  PNG images cannot be animated like GIF images. However, the related.MNG format can be animated.  PNG images do not provide CMYK colour support because they are not intended for use with professional graphics.