The term ``voltage divider'' refers to a circuit configuration in which there are two resistors (or resistor networks, or, as we will see later, two impedances) in series with a voltage source, and we are interested in the voltage between the resistors. We'll see lots of examples of this kind of configuration.
The expression
, the ``voltage divider
equation'', relates the voltage 
at the point between the two
resistors to the voltage 
of the supply.