Voltage at a Point: Understanding Ground in Circuits

[quantum13]

I was reading a book on circuits and came across the phrase "a voltmeter can measure the voltage at a point with respect to ground"

I don't actually understand what this is supposed to mean in circuitry though. Don't people usually refer to the voltage drop across a resistor?

I suppose this could be a homework question so mods can move it; in that case there is a simple circuit with battery and a resistor, how do you calculate voltage "at a point" in between?

edit: i realized that "ground" is just an arbitrary point defined in a circuit, i missed that part reading it hehe

 

[Dickfore]

ground is a common reference point that is chosen arbitrarily in the circuit. If there is only one EMF source, it is customary to be attached to its negative end.