Gothic can refer to three different, but vaguely related things.
1: Various ancient Germanic tribes of Europeans whose numerous sackings of Rome helped bring about the fall of the Roman empire.
2: A type of horror literature written in 18th and 19th century Europe featuring gloomy old castles and ruins, lost loves, terrible weather, and, occasionally, vampires.
This literary movement is distantly related to the terrible adolescent fashion trend that includes pale makeup, black hair dye, terrible music, and lots of angst.
None of these things have much direct connection to Gothic buildings, for which we need to turn to Gothic’s third, and most useful definition for our purposes: an architectural style developed in Northern Europe, specifically France, during the late medieval period that features the use of pointed arches.
Pointed arches are so characteristic of the building style they are also called Gothic arches.
There is, of course, a bit more to Gothic architecture than that, but for our purposes, just remember that the easiest way to identify a Gothic building is to look for pointed arches in the windows or the ceiling vaults.