ICO is a format (full name - Icon File) of bitmap images and refers to system files. Developed by Microsoft and designed to store icons in its operating system. ICO files, as a rule, store icon images - modest in size, with a small resolution (from 16x16 to 64x64 pixels), with different color depths (from 16 colors). In the graphical interface of various operating systems, ICO format files are used to display files, programs and folders (primarily in Windows) or as an icon for a specific website.
GIF is one of the most common raster image formats. Its name is an abbreviation for Graphics Interchange Format File. The developer is the CompuServe organization. A feature of this particular image format is its ability to support the animation function. You can edit animated GIFs in different programs (for example, Easy GIF Animator). Animation is achieved due to the fact that a file of this format carries in itself in a certain sequence several raster images at once. With a depth of up to 256 colors, significant data compression in GIF files is possible without loss of quality.