"Wo ist sein Schuh?"

Translation: Where is his shoe?

[2708_2013]

so sein means his and ihr means her?

[mizinamo]

Yes (at least as possessive determiners).

[TomHetzler1]

Ihren would be her, i believe. But yes sein is his.

[mizinamo]

Well, "her" can be ihr, ihre, ihren, ihrem, ihrer, ihres depending on the gender, number, and case of the possession.

[NiiOkaikoi]

So in which instance does wo mean what since was also means what