1. Potential Difference vs EMF
You may previously have used the term 'voltage' but now you need to understand the difference between the EMF of a supply and the PD across a component. Please note that this analogy is not perfect, it doesn't really explain how energy can be transferred almost instantaneously or how alternating current works but it's a start...
2. The Volt and W=QV
How can you define the volt?
'1 volt is the potential difference between two points when 1 joule of work is done to move a charge of 1 coulomb.'
'1V is the PD across a component when 1 joule of energy is transferred per coulomb of charge passing through the component.'
3. The Kinetic Energy of Electrons
The energy gained by charged particle moving through a potential difference can be converted into kinetic energy. This is the basis of old style TVs, oscilloscopes and also particle detectors.
4. Kirchhoff's Second Law
This will help you to understand Kirchhoff's 2nd Law when you consider the conservation of energy in a circuit.