Waypoints are, in simple terms are sources of longtitude and latitude (or altitude) that identify where one is. Almost like terrain marking (the most basic way to explain it is if you were hiking w/o GPS you'd make markings like; a big rock, dead tree, waterfall...etc). Nowadays it more abstrac like artificial beacons, and no real physical pairings, but more mathmatical related to numbers (latitude/longitude/altitude)