node.tpl.php

node-forum is the template that's applied to a forum node. Similarly, if you had the file node-blog.tpl.php that would be applied to the blog type.

This mechanism of phptemplate provides an easy way to style a particular node type without needing complex if/else statements in the main node.tpl.php file

node-forum.tpl is used for forum type nodes and node.tpl is default node theme (used when there is no spesific node theme file)

forexample lets say you have a site with forum you can have such node.tpl for your nodes

<div id="node-<?php print $node->nid; ?>" class="node">
<?php if (!$page): ?>
  <h2><a href="<?php print $node_url ?>" title="<?php print $title ?>"><?php print $title ?></a></h2>
<?php endif; ?>

  <div class="meta">
  <?php if ($submitted): ?>
    <span class="submitted"><?php print $submitted ?></span>
  <?php endif; ?>

  <?php if ($terms): ?>
    <div class="terms terms-inline"><?php print $terms ?></div>
  <?php endif;?>
  </div>

  <div class="content">
    <?php print $content ?>
  </div>

  <?php print $links; ?>
</div>

meanwhile you can have a node-forum.tpl like this

<div id="node-<?php print $node->nid; ?>" class="forum-node">

<?php print $picture ?>

<?php if (!$page): ?>
  <h2><a href="<?php print $node_url ?>" title="<?php print $title ?>"><?php print $title ?></a></h2>
<?php endif; ?>

  <div class="meta">
  <?php if ($submitted): ?>
    <span class="submitted"><?php print $submitted ?></span>
  <?php endif; ?>
  </div>

  <div class="content">
    <?php print $content ?>
  </div>

  <?php print $links; ?>
</div>

Not that user picture is hidden at default nodes while taxonomy terms are hidden at forum nodes. These are just basic samples by using devel or contemplate modules you can have a better knowledge about node variables especially if you use CCK.

And sweet CSS again note I defined node as class for default nodes while I defined forum-node for forum nodes. As you can easily guess

.node h2{} will style node titles and
.forum-node h2 will style title of forum nodes

this thread smells like spam...