This is the 17555th most frequent Russian word.
трехэтажный
Three-story (referring to something with three floors).
In this sentence, 'трехэтажный' is used as an adjective to describe a 'дом' (house) with three floors or stories.
Мой друг живет в трехэтажном доме.
My friend lives in a three-story house.
Here, 'трехэтажный' qualifies 'офис' (office), indicating that the office space spans three levels.
Мы недавно построили трехэтажный офис в центре города.
We recently built a three-story office in the city center.
In this example, 'трехэтажный' describes 'паркинг' (parking garage), showing the concept of a structure designed across three elevations.