Electricity is commonly seen as the movement of electrons.
Voltage is defined by how much energy each electron has as it moves. The voltage of a battery is defined by the elements in the positive and negative side (cathode and anode). For example, Zinc/Manganese oxide in our alkaline batteries gives us a voltage of 1.5V.
Current is expressed in Amps (A). It quantifies how many electrons are flowing per second.
The capacity of a battery defines how much total energy is stored in each battery.
The power output of a battery is how much energy a battery can give at a given time. This is a very important factor as it defines what you should use the battery for. High drain devices (such as cameras) require a high power output battery (such as our Ultra range batteries). Low drain devices (such as remote controls or clocks) only need a small amount of power to function.