A waypoint ID (or waypoint code) is an alphanumeric code of typically 4-8 characters (letters and digits) in length, used to reference a waypoint.
In GPS receivers, a waypoint ID is automatically created when for example the current location is stored as a waypoint. For example, my Magellan GPS uses codes in the sequence WPT001, WPT002, etc.
In geocaching, a 6- or 7-character code is used to identify each geocache. The coordinates corresponding to the waypoint ID may be the location of the cache container (for a Traditional cache), the starting point for a Multi-cache, or a reference point for a Mystery cache.
The first two digits in a geocaching waypoint ID typically identify the cache listing website on which the cache is hosted, as follows: