All houses (well with some exceptions) have walls, a roof, doors and windows, but they aren't all the same. How they're designed depends on a lot of different factors, such as: who will live in it and how they'll use the rooms, where the house will be built and what's around it, and what materials will give the best finish or last the longest.
Our houses aren't only the result of professional architects. We spend our time in them making them work the way we like, and also sometimes just making them work. Finding the best place to put up shelves, where we put a mirror, the type of furniture we use and even those little fixes like the superglued piece of plastic that keeps the cabinet door closed or the particular way of stacking cans in the cupboard to make sure they all fit.