ここは免税店ですか。

here (place physically close to the speaker, place pointed by the speaker while explaining); this place; these last (followed by a duration noun and a past sentence: time period before the present time of the speaker); these next ... (followed by a duration noun and a non past sentence: time period after the present time of the speaker); the next ...

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

duty-free store

be; is

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way