Questions & Answers about chuāngkǒu zài nàbiān.
Because 在 is the normal verb for showing where something is located.
- 窗口在那边。 = The window is over there.
- Literally: window + be located at + that side
Chinese usually uses 在 for location, not 是.
Compare:
- 窗口在那边。 = The window is over there.
- 窗口是新的。 = The window is new.
So 是 links a subject to a noun or adjective-like idea, while 在 tells you location.
那边 means over there, that side, or in that area.
It is made of:
- 那 = that
- 边 = side, edge, area
So 那边 is a natural way to point to a general place that is not near the speaker.
It is slightly less precise than a specific location like 房间里 (in the room), but very natural in everyday speech when pointing or indicating direction.