When you boil something down, you remove liquid from it and reduce it to a concentrated form.

当你熬东西的时候，你要把里面的液体蒸发掉，然后把它制成浓缩状态。

But in conversation, when you boil something down, you get to the most important part of a problem or a situation.

但是在对话中，当你boil something down时，就是说你直指某个问题或者某种状况最重要的部分。