Each cache in the database is represented by a graphic that indicates what sort of cache it is: traditional, multi, webcam, virtual, and so on. You can find a full description of these icons here
Cache Icon Graphics - Copyright 2006, Groundspeak, Inc. - Used with permission
If GSAK does not recognize the cache type as one of the known Groundspeak types, the it will be allocated the "O" (other) type with the icon of:
