Not really understanding forum subscriptions

[Picture North Carolina]

I understand subscribing to threads, but not to forums. I've read the faq and other stuff, but cannot find detailed info.

Can somebody explain (or link) forum subs?

Here's what I thought it would do and what I desire: after subscribing to one or more forums, come back at a later date and click a link that will show new posts only in the sub'ed forums. But I don't see that link anywhere. Thanks.