Exactly how does caching work?

[Frank Rizzo]

I am new to asp.net, so this might be a dumb question.
If I place the <%@ OutputCache Duration=" %> into the master page, will
all the pages that happen to be a part of that master page be cached?

If I place <%@ OutputCache Duration=" %> into an ASPX page that will be
a part of the master page, what exactly will get cached?

How do I set the cache Duration to be forever?
How do I programmatically remove the page (or master page) from cache,
particularly if the page has querystring parameters?

Thanks.