In other words:
You can think of a Bone in Edit Mode as a single Edge; it has two Vertices at the ends. You can move one Vertex (‘ball’), or both (the whole Edge) at the same time. Moving one Vertex (‘ball’) is Scaling and/or Rotating that Edge (Bone).
The big difference is with Snapping; if you Snap an Edge to the 3D Cursor (or to something else), it will collapse that Edge into a single point, whereas Snapping a Bone will Move the Bone, so that its Head (the “big end’) is at the snapping point.
