Thanks QBasicJedi for your explanation. That makes sense. For those readers who did not understand QBsicJedi's detailed writing, I will simplify what I understood.  "When you look at a crescent moon, the poles are at the intersection of the two arches – one the outer boundary and the other formed by the terminator. However, the way an observer see these points “up or down” depends on where he stands on earth and which direction he looks at the moon.