Learn German: Wo ist die Apotheke? - Where is the pharmacy?

In German, you use ist (is) to ask for the exact location of a specific thing, like die Apotheke (the pharmacy). You use es gibt (there is/are) to ask if something exists in general, like Gibt es hier eine Apotheke? (Is there a pharmacy around here?).

Is die Apotheke in the accusative case here?

No, it is in the nominative (subject) case. Even though your current lesson focuses on es gibt which requires the accusative case, the verb used in this sentence is ist (is). The verb sein (to be) always connects to the nominative case.

How do I know that Apotheke uses the feminine article die?

A very helpful rule of thumb for beginners is that German nouns ending in -e are usually feminine. While there are some exceptions, seeing that -e at the end of Apotheke is a great hint that it takes die.

I keep mixing up wo and wer. Does wo mean 'who'?

No, wo means 'where'. This is a classic false friend for English speakers because it sounds so much like 'who'. If you want to ask 'who' in German, you actually use the word wer!