Ohm's law describes the
relationship between voltage, V , which is trying
to force charge to flow, resistance, R , which is resisting
that flow, and the actual resulting current I .
The relationship is simple and
Thus large voltages and/or low resistances produce large currents.
Large resistors limit current to low values.
Almost every circuit is
more complicated than just a battery and a resistor, so which
voltage does the formula refer to? It refers to the voltage across
the resistor, the voltage between the two terminal wires. Looked at
another way, that voltage is actually produced by the resistor.