This is the 39th most frequent Polish word.
gdzie
"Where."
The word 'gdzie' is used as an interrogative pronoun asking about the location of someone's residence.
Gdzie mieszkasz?
Where do you live?
The word 'gdzie' introduces a subordinate clause indicating the unknown location related to the action.
Nie wiem, gdzie idzie.
I don't know where he/she is going.
Here, 'gdzie' functions as a relative pronoun connecting the location to its description.