What does a negative voltage indicate in a circuit or measurement?

what dose a negative voltage mean?

Found while googling...

When we measure voltages in a circuit, they are usually referenced to a common node in the circuit called "ground". Ground does not have to be connected to earth. It is just a term that indicates the common node in the circuit.
The schematic below should help explain this concept. As you can see, whether a voltage is positive or negative simply depends on which end of the battery (or other power supply) is connected to ground.

Well my view on ur question is , Negative voltage or positive voltage is the point(node) which drives the circuit!
For say in a diode , to forward bias it we need to attach a positve voltage to the anode because we need the positive ions of the battery to repel the positve ions(holes) in the diode(according to conventional flow)
thus indicating a flow .now what I spoke of is a positive voltage .
Now in negative voltage , the voltage terminal where the positive ions are terminated (according to the conventional flow) is the negative voltage!!!
Because at positve voltage we can expect a positive ions outcome and at negative voltage we see a postive ion temination(recombination)
this is the phenomenon seen in battery!!
But the outline of -ve voltage is a vltage lesser to a higher potential(+ve voltage).as we see at this point(node ) the elctrons coming out so it is a negative voltage .
Note: GROUND AND NEGATIVE VOLTAGE ARE DIFFERNT , GROUND CAN BE ANY VOLTAGE AND OTHER VOLTAGES ARE MEASURED RELATIVE TO THAT REFERNCE VOLTAGE AND HERE IN THEIS SCENARIO -VE VOLTAGE IS THE ONE WHICH IS VERY LESS THEAN THE REFERNCE VOLTAGE!!!!!!!!!