what 什么（东西）.指的是物体——可以是具体物体,也可以是某种内容（比如说话的内容）
where 什么地方.指的是地点.
因此对初学者来说,可以很简单地依据意思去判断,what 引导的从句就是表示说明“物体”的——或者说是“物体”的扩展说明.what引导的从句可以是宾语从句,也可以是主语从句——也就是说,“物体”
例句：What he said is very interesting.他说的东西很有意思.
这里What he said就是主语从句
例句：I realy like what he has shown us.我真的很喜欢他展示的东西.
这里what he has shown us就是宾语.
而where引导的从句就是表示“地点”的,或者说是“地点”的扩展说明.地点都是做状语的,所以where引导的从句也是作状语的.
例句：Is this the place where you have been yesterday?这是你昨天到过的地方吗?
分析：place,地方；where引导的从句就是place的具体扩展说明.
which 表示“哪一个”,在一定范围内特指的人或物.
Which one do you like better?你更喜欢哪一个?
例句：I will buy the red laptop which my wife like very much.我要买我老婆很喜欢的那个红色笔记本电脑.
分析：这里which my wife like very much是定语从句,修饰laptop
如果用“介词+which”引导的定语从句,修饰表示地点的名词,那么“介词+which”可以替换成where,从而变成地点状语从句.比如：
This is the street in which my brother met his wife in 2004.
= This is the street where my brother met his wife in 2004.
这就是2008年我弟弟遇见他老婆的那条街道.