What is the difference between potential difference and voltage?

They are the same.  PD is not the difference in voltage, it is the voltage.  

Voltage is the measure of difference in electrical potential in two points.  What your teacher is talking about is Voltage Difference.

diff of potential is the actual voltage between two points...like your meter leads, measuring voltage. they are basically the same thing...

I think physicists like potential difference and engineers like voltage. In 30 years as an engineer, my Dad never used or heard the term potential difference. Voltage difference, yes.

Your teacher is slightly mischaracterizing it. "Electric Potential" and voltage are the same thing, but the terminology is easy to confuse.

It's a measure of the potential energy that a charge would have if it were in a given location. You can find the electric potential by knowing certain things about the location (such as the other charges in the area). But you need to know the size of the test charge to know what the actual potential energy would be, the Electric Potential only tells you what the potential energy could be.

Note, it's a bit confusing because the analogues to mechanics don't make as much sense with potential difference as they do in other areas of electromagnetism.

Voltage its the current term and potential difference is the scientific term. Voltage (or PD) its not a feature of a corpse. It is a reallation between several corpse (generaly 2). The potential is the work needed for a particle from the infinite to be atrated to a particular point in a space where there is a electric field, a PD is the work needed for a particle to go from one particular point with a certain potential to another with other value of potential. With the Ohm law its possible to determinate the current of a circuit knowing the PD (V=RI).

voltage is the measured value
potential is what it could be
potential is rarely used in engineering

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potential difference = voltage. As simple as that. The term 'voltage' is commonly used to describe the 'voltage difference' between two points, as in one point is at 110 volts and the other at 0 volts, for example. The voltage or voltage difference between the two points would be 110 volts; the potential difference between the two points would also be 110 volts.