Learn Arabic (Modern Standard): أين الأب؟

In Arabic, we do not use a word for 'is' or 'are' in the present tense. To say 'Where is the father?', you literally just ask 'Where the father?' (أين الأب؟).

How does أين (where) work with nouns?

It goes at the very beginning of the sentence. Because there is no 'is', أين is immediately followed by the noun you are looking for. Notice that the noun usually has ال (the) attached to it because you are asking about a specific person or thing.

Why is there a little symbol over the second vertical line in الأب?

That symbol is a hamza (ء). When you attach the word for 'the' (ال) to 'father' (أب), the hamza shows you that you must pronounce a distinct, crisp 'a' sound for 'ab'. You pronounce the whole word as 'al-ab'.