Does a window's handle change everytime the parent window is closed and opened?

I have a "hWnd spy" program, that informs me of a specific window's hWnd. However when a program is closed and then lauched again it's hWnd and all child hWnd's are different.
Now either the "hWnd Spy" program is either providing me false information or my suspicions concerning hWnd's changing, is true. Can anyone end my madness and kindly tell me the answer, please and thanks?

p.s. If hWnd's do periodically change, How can I make my program get the handle of a specific window? (I know this is asking a lot )

Daniel Christie