>Initial values specified for x, y, ... are evaluated before x, y,... are cleared.

It's from the **Details** in [The reference to Block][1]. And I can't understand it. 

When are the local variables cleared and what's the meaning of "initial values are evaluated"?

Could anyone give an example to illustrate it? Thanks a lot!


  [1]: https://reference.wolfram.com/language/ref/Block.html