An icon is actually a collection of multiple images in different formats, and contains a certain amount of transparent area. Because of the diversity of computer operating systems and display devices, it is necessary for icons to be sized in multiple formats.
When an operating system displays an icon, it selects the image of the icon that best fits the current display environment and state according to certain criteria. If you are using the Windows 98 operating system, and the display environment is 800x600 resolution with 32-bit color depth, the image format you see on your desktop for each icon is 256-color 32x32 pixel size. If you are in the same display environment, Windows XP operating system, the image format of these icons is: true color (32-bit color depth), 32x32 pixel size.