as introduced in Pose and Armature independently
Not sure what you mean exactly, but here’s an overview:
In Pose Land:
A pose is exactly that. It holds all the posebones for a current pose. In Blender its equivalent to the actual pose your character has (think actions and the pose library).
Posebones are what you actually use to manipulate the pose by rotating, scaling, moving, etc.
In Armature Land:
Bones are just opaque bone objects. If you only need to read/write about where bones are and how there oriented (and some other things) then you’d use this.
Edit Bones let you “put” the armature in edit mode and add bones and manipulate these new bones.
Armatures are just dictionaries, essentially, that give you access to the bones.
That’s a simplifying it a little, but if you read the API and play with it, you can probably figure it out. PapaSmurf has worked extensively with this part of the API. He might can give a better explanation than that if it doesn’t make sense (or I left out a critical detail). Its probably one of the more confusing parts in how fragmented and wonky certain areas are.