Changes to index in WP1.3

Hi there,
I just updated my CVS version and noticed there was an index update.
Could you tell me what differences have been made?
I notice that this old line (below):
<?php if ($posts) : foreach ($posts as $post) : start_wp(); ?>
has been replaced with this one:
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
What is the difference?
Thanks