The sidebar.php file usually consists of only minimal markup needed for outputting the widgets in the side-column widget area, which was registered in functions.php. You can do that with dynamic_sidebar(), and by passing the ID of the widget area wanted, which is side-column, again as registered in functions.php.
This means that the sidebar.php is pretty straightforward to say the least.
<?php dynamic_sidebar( ‘side -column’ ); ?>
</section><!-- #sidebar ends -->
You can also have conditional sidebars (i.e. this site), that change content based upon what page/post is being requested.