png PNG stands for portable network graphics. It is the raster graphics format associated with the .png filename extension. Unlike GIF format, the limitation of 256 colors does not hold with the PNG format. In fact this among other reasons was the motivation behind development of the PNG format to improve upon the GIF format. The PNG format however uses a single image format and thus does not support animations. Because the format was engineered to ease the distribution of graphic files across computer networks it is also not well suited for professional graphics.
ico The .ICO filename extension refers to the ICON image file format originally developed by Microsoft. The extension is used to represent computer icon images of varying sizes designed for the operating system Microsoft Windows. Its use today has extended to developing icons for programs designed using the Microsoft developer's suite Visual Studio and other applications. Similar to other device independent bitmap file formats, the ICON file format is also in the raster graphics class of image formats where each individual pixel is part of an orthogonal dot matrix data structure with support for a limited palette of color information. As a resource file, the .ico file format has its strength in contextual use. This allows for multiple icon images of different color depth or size to be stored within the resource file and used when appropriate.