This is an archive file used on Macintosh computers. It stores branched resources and data in the file system as one file. It includes the storage of fonts and convenient loading of data with Macintosh to the Internet to be transferred to other Mac devices. It’s used to import PostScript Type 1 program language data.
ICO is a file of this format usually contains a small image icons of different resolutions (16x16, 32x32, 64x64 pixels) and various color depths (16 colors, 32, 64, 128, 256, 16-bit, and so on). Used to display files and folders in the graphical user interface (GUI) operating systems. This format can be opened with the help of the program ACDSee.