As pointed out, most of the functions that the master of the house would be involved with took place on the ground floor and the floor above it, with the attic and basement confined to service functions. Note however, that the 'ground floor' in this case might actually be raised up above the ground considerably. This is especially the case in city houses. Country houses not so much.
The first floor would have the reception spaces; the parlor, the drawing room, the smoking room, the billiard room, the dining room, the ball room, whatever. The second floor would have the master's rooms and his family's rooms. Husband and wife would often have separate rooms. There would often be an office or library on this floor, though this one might be on either floor.
Now a country home might have some or all of the second floor functions on the first floor, land not being as confining, and the whole situation being less formal.