CUR is a Microsoft Windows cursor format.
CUR files can have multiple icon images of different sizes in the same file, so that programs displaying them can pick the size that is appropriate for a particular use. Image data within the file is either in BMP or PNG format, with some header bytes defined by the CUR standard.
ICO (icon) files are in a nearly identical format with only a few bytes different.
- ICO (Wikipedia) (also describes CUR)