When talking, for example, about an apartment building, you ca say "The building has eight floors". But when talking about a house that got two "floors", do you still call them floors in English? Or is there a different word for "floors" in a regular house?
Note that there is a difference between UK and US usage with respect to numbering floors. A two-storey building in the UK is said to have a ground floor and a first floor. In the US the same building would be described as having a first floor and a second floor.
In Britain, when we are talking about a two-storey house (home), we normally speak about 'upstairs' and 'downstairs'. In a two-storey commercial building we might (in Britain) talk about the ground floor and the first floor.
Note also that 'storey' in the UK is spelled 'story' in the USA.