Question

定语从句中什么时候用where详细点

Answer 1

先行词是表示地点，场所，环境类的名词或代词，并且，先行词在从句中做低点状语时，选用关系代副词where。例如
This is the factory where his father once worked.

Answer 2

where==表地点的介词（如：in，at，on，under等）+which
E.g. :
Can you tell me the office where he works? (where=in which)
你能告诉我他上班的办公室吗？
where实际运用有点复杂，从先行词为明显的“地点”转为“地点的模糊化”。事实上，对于where这个词，不能只理解为表地点。当先行词表示某人／物的situation，或某事所发展的stage，或表达某事的某个方面时都可用where这个关系副词。如：
They have reached the point where they have to separate with each other．
他们已经到了必须分手的地步。
We are living in an age where many things are done on computer.