So there's A城 B城 and X市 Google says 市 and 城 are both cities, but will I be right to say it's District A and B of City X?
I realized more things while trying to type my context explanation they're indeed different cities, but thanks for responding
城 is city, yes but 市 is something like a regional capital. On the other hand, there are very wide range of "regional capitals", ranging from things like an aristocratic/feudal "Baron's city under a Duke's regional rule" to "in name only" administrative convenience, so like nono said, context matters.