No it wont explain units. This video explains basics of li ions and then moves to advanced level. It is assumed that viewer know about these basics.
I can do it here
Ohm's law: V = IR (V is voltage, I is current, R is resistance)
Power (Watt) = Voltage (V) x Current (I, or Amp)
Energy (Watt-hour) = Voltage (V) x Current (A) x hour (h)
With these basic equations you can roughly get an idea of energy stored in a device.
when li ion capacity is said in mAh unit, it don't tell the voltage and is misleading since the voltage will tell you the energy that is stored in it. Also important is the discharge rate (A/sec) that is used. Higher discharge rate will result in lower energy (due to increased resistance).
If you have any specific question, I can answer it in simple terms.