I've been reading a number of materials trying to understand the physics that allow electricity to be possible. I'm confused by this virtual positive [charged] particle (often called a test particle) that is used to explain the direction/properties of an electric field and thus the movement of energy in a circuit.
Specifically, I recognize that the energy is loaded onto this virtual positive particle by the virtue that Work and thus a gain of Energy is required for the positive particle to move from the anode side of the battery back to the cathode side of the battery (where the energized ions are present). From this point the positive particle (now energized and at the point of high energy at the cathode) move to the point of low energy (the anode) offloading their energy onto a load which transforms it into some other form of energy (thermal in the case of a short circuit or resistor load).
I'm curious though how does this positive particle move in any direction? With a classic electronic circuit (copper wires) the electrons are the charge carriers and thus form the charge highway/sea of electrons allowing energy to move (in response to a induced electric field). i.e electrons move, atoms/ions do not.
Is this simply a convention (much like conventional current vs electron current) in that the ions are not moving but the illusion is given that they are by virtue of the electrons moving and leaving holes/positive charges in their wake (in the opposite direction)? Is so why was it chosen instead of using a negative charged particle and thus being easily traceable by the movement of electrons?