A detached house is a residential building which is intended for a single household, e.g. free-standing houses.
An apartment is a housing unit in a building with at least two floors, three housing units and normally a shared entrance. Typical examples are apartment blocks and terrace apartments.
Small houses are residential properties which are typically physically connected through at least one shared wall, and possibly also a shared floor/roof, with the neighbouring dwelling. Typical examples are terraced houses and semi-detached houses. Detached houses in a series/chain are also considered small houses.