Calling Templates and Post Summaries

I had this well written and then my browser crashed.

OK so. My first prob is this. I’ve been reading but I’m overwhelmed and confused right now. How do I call a template??? I’m sure this is a really simple problem but I can’t find the solution, or at least I can’t recognise it. I tried at first to create template (“Latest Posts”) and then use it when creating a new Page from the admin, but that wasn’t right b/c all that did was to pull up the title of the page and NOT the posts that I’d created like I want it to. Kind of like this: http://www.cnn.com/24hours/

A thousand apologies if this has been asked and solved, but I’m not even sure where I’m looking anymore.

Also, is there a specific reason why I can’t pull posts from the template? Or am I going about this totally backwards? I just want a link in the sidebar that says “latest posts” which points to a new page with the posts listed (with excerpts) chronologically.

The other thing is the code. I am using this:

<div class="entry">
  <?php if(is_category() || is_archive()) {
     the_excerpt();
 } else {
     the_content();
 } ?>
</div>

to pull up the excepts (with no meta or ‘read more’ links), but I can’t find out if this is right because of my first problem. Any links to already resolved posts and other help would be greatly appreciated. Please and thanks…