This is a format for presenting fonts in PDF files that was initially conceived to store symbols in the Japanese and Chinese languages because it had a 16-bit structure and allowed for more precise adjustment. CID expands the the potential for PostScript by supporting languages that do not have a left-to-right orientation, and by supporting even a vertical mode of orientation.
This format is used to store small personal icons. It is used in website development to create favicons that are displayed in the address bar of the web browser as well as in satellite TV for identifying broadcast channels. It is very similar in structure to a GIF format image.