[HarryD]

If you do not have a complete circuit (i.e. a continuous connection) from the positive battery terminal to the negative batery terminal, you will not have electrical flow (current). Each circuit in your car has this.

When you use a tester like a test light or voltmeter, you usually ground one tester lead (which is connected to the negative battery terminal) and touch the other lead to where you expect to see power. If the circuit (path) from the battery positive terminal to the point where you touched the lead is continuous, current will flow and will be evidenced by the lamp lighting or the meter showing voltage. You can move along the circuit to various points to determine if the circuit is intact or not. If the circuit goes dead at some point, the fault is between the last good point and the dead point.