The upper floor; upstairs — the floor above within a building.
荷物は階上の部屋に運んでおきます。
I'll carry the luggage to the room upstairs.
階上の住人から苦情が来たので対応した。
We dealt with a complaint from the upstairs resident.
非常階段を使って階上へ上がった。
I went up to the upper floor using the emergency stairs.
The top of the stairs — the place reached after climbing a staircase (the stair landing or uppermost step).
階上で音がしたので、確認しに行った。
I heard a noise at the top of the stairs, so I went to check.
荷物を抱えて階段を上り、階上の踊り場で一息ついた。
Carrying the luggage, I climbed the stairs and took a breather on the landing at the top.
階上から眺める景色はなかなか良い。
The view from the top of the stairs is quite nice.