The Microsoft Windows Icon format is used on Windows for displaying icons. It supports multiple icon sizes and color depths.
A related format is the Microsoft Windows Cursor. The export dialog shows all the icons available. For each icon size, there are several settings that can be changed.
For each icon size you can select in what format it should be saved. The available choices are:
Indexed format with only two colors.
Indexed format with only 16 colors.
Indexed format with up to 256 colors.
For RGB without alpha channel.
The most common format is RGB with alpha channel.
When checked, the icons are saved as compressed PNG images. Note that not all programs support reading this type of icon.