Question: I have learned that when someone wants to know where a person comes from, one must ask: 

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> Woher kommen Sie?
> 
> 
> 

A lot of people have asked me: 

> 
> **Wo kommst du her?**
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> 
> 

or 

> 
> Wo kommen Sie her?
> 
> 
> 

Indistinctly. So the question is what is the difference?

Answer: 
The difference is in the meaning, but this can change by adding words.

The first phrase *Woher kommen Sie?* asks
more where you are coming in the moment. For example: *Ich komme gerade aus der Universität*. But it can **sometimes** also have the meaning of the second, depends on the context. So standard meaning: From where do you come in the moment?

In the other phrase *Wo kommen Sie her?* one asks about your origins, town or country. So standard meaning: From which town/country are you?

But the phrases can be modified. If I ask *Woher kommen Sie **eigentlich**?*, then it has the standard meaning of the second. If I ask *Woher kommen Sie **gerade**?* underlines the meaning, where do you come in the moment.

And if I ask *Wo kommen Sie **denn jetzt** her?*, the second has the standard meaning of the first.
"Woher kommen Sie?" is a more formal and slightly outdated version of "Wo kommen Sie her?". Both mean "Where are you from?" (or literally, "Where do you come from", as in "what place/event were you at before you arrived here" but it is less often used to mean that).

"Woher kommen Sie?" is not used in spoken language very often, as far as I'm aware. (I'm German, from the Cologne area). It sounds stilted.