例1：This is the place where he works(这是我工作的地方）因为work是不及物动词,后不可跟名词或代词,所以连接词用副词性连接词where,充当he works的状语.例2:This is the place which we visited(这是我们参观过的地方）visit是及物动词,后面必须有宾语（就是后面必须要有东西跟着）.及物动词在从句中若无宾语,则需要可充当成分的连接词连接,这里用which.给你补充点知识：状语从句与定语从句的区别在于定语从句有先行词.例：1）定语从句This is the place where he works中the place=where(指这个地方)即the place是先行词2)状语从句I will tell him where i will work中where≠him即无先行词
总的来说：where 引导的定语从句表示地点,which也可以表示地点.区别在于where是副词,前面不能加介词,而which是代词,需要加介词.
例如,which:the house which I live in.也可以说the house in which I live.
where:the house where i live.不可以加in
