all that 和 what 辨析？

That's all that they have done.

That's what they have done.

请教老师，以上2句不同在哪呢？ 麻烦老师多讲讲，谢谢！

what=the thing which . 所以，

That's all that they have done.

That's the thing that they have done.

不同就是all 和 the thing 有什么区别。这不是非常明显的吗？其实你一个人都要可以做出如此的剖析的。