Change Site Title and Description html tags if not home page

by 

<?php if (is_home() || is_front_page()) { $header_tag = 'h1'; }
    else { $header_tag = 'h2'; } ?>

<<?php echo $header_tag;?>><?php the_title();?></<?php echo $header_tag; ?>>

Expanding on what Stephen Harris said, here is a useable example. Lots of different ways to use same code function.