Comment loop: how to add to a “page”.

Forgive me if this question has already been answered, but I did search extensively for a solution and could not find one.

I understand that a comment loop begins with:

<?php foreach ($comments as $comment) : ?>

and ends with:

<?php endforeach; ?>

However, I am sure someone must be able to explain to me what I must put before all of this to make it work. I have used The Loop quite successfully, even using it multiple times in one page, but I simply cannot make the Comment Loop work.

To expand just a little further on my situation: I need to display comment excerpts and author names as well as their gravatar (I believe I can figure this out, so no worries there) on the same page which I have coded to display a list of recent posts.

Thank you very much.