definitions

• Potential difference is the work done per unit charge moved between 2 points
• a column is the amount of charge passing a point in 1 second if the current is 1 A
• Conventional current is the flow of positive charge.

  This is simply a rule (convention) - the direction of current does not affect the size of current /voltage /readings in a circuit.
• Load - is the term used to describe the combined effect of all the items such as light bulbs, resistors that cause charges to do work/transfer energy - known as total resistance.
• Terminal potential difference: it is the voltage measured across the terminals of the battery when current is flowing through the circuit when the switch is closed.  It represents the work done per coulomb of charge for the entire circuit - also called Vload and is less than the emf.