Diff between bloginfo( 'name' ) and bloginfo( 'description' )?

I’m trying to replace the site header and tagline with category name and description, based on post category.

The code, below, works fine on category pages. It replaces both the title and the tagline.

On posts within a category though, the category name replaces the site headline, but the category description doesn’t replace the tag line.

Here is a category page (works right): http://miketurco.com/consulting-services/

Here’s a post within a category. The title is replaced but the tagline is not:

http://miketurco.com/vendor-referrals-and-management/

This is the code:

<?php if (is_category() || is_single() ){ ?>
                    <span class="home-link">
                    <h1 class="site-title"><?php the_category(' '); ?></h1>
                    <h2 class="site-description"><?php echo category_description(); ?></h2>
                    </span>
                <?php } else { ?>
                    <a class="home-link" href="<?php echo esc_url( home_url( '/' ) ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
                    <h1 class="site-title"><?php bloginfo( 'name' ); ?></h1>
                    <h2 class="site-description"><?php bloginfo( 'description' ); ?></h2>
                    </a>
                <?php } ?>

Thank You!