Waypoint
A Waypoint is a location on Earth defined by a set of coordinates. When stored in a GPS receiver, or identified on cache page, a waypoint is typically referenced by a waypoint code (or waypoint ID).
In geocaching, traditional caches have a single waypoint - the location of cache (or ground zero).
Multi-caches have more than one waypoint, with the final waypoint being the cache. In cases where a second (or subsequent) waypoint is found by projecting a bearing and distance from a first waypoint, this is refered to as a projected waypoint
Waypoints in geocaching are typically two-dimensional, referenced by old latitude and longitude coordinates. Altitude is ignored, as caches are typically at or near ground-level. (This unknown dimension is exploited for sneaky effect in some caches.)
