British versus American English—The Floors
A speaker of American English, talking about the different levels in a building, might say that there’s a conference room on the first floor and two on the second floor.
A speaker of British English, would say that there’s one conference room on the ground floor and two on the first floor.
The British call the floor of a building at street level the ground floor (the floor in contact with the ground), whereas the Americans usually call it the first floor.
That can cause a little confusion! 😉