了解“这个”约束

我正在阅读“ Eloquent Javascript”这本书，并且在“对象的秘密生活”一章中。 作者说：

"since each function has it's own bindings, whose value depends on they way it is called, you cannot refer to the this of the wrapping scope in a regular function defined with the function keyword.

我不明白他所说的“包装范围”是什么意思，请您解释一下并提供一个简单的例子吗？