Mirror, Mirror on the wall

I never know what to call the place I live in. Is it an apartment, a townhouse, a fourplex? It's a fourplex because there are 4 units in this place, it's an apartment because my address says "apt. C" and it seems like a townhouse because it's 2 story, our bedrooms are upstairs. Anyway, the problem with living in a multiple-family dwelling is that you share walls with your neighbors which means