Hooking Windows.

Could someone explain to me what hooking is and how it is used? I have looked a few sites and I have seen a lot of information about hooking, but no explanations as to what it is useful for.


Thanks.

it could be useful to restrict the size of a form.
Setting the width and hight in the resize gives ugly results(it still resizes but snaps back)

Here is an example:
http://www.mvps.org/vbnet/code/subclass/minmaxinfo.htm

Is hooking and subclassing equivalent then?