Archive page layout

I found this snipet of code in another thread:

add_filter('avf_blog_style','avia_change_category_blog_layout', 10, 2); 
function avia_change_category_blog_layout($layout, $context){
if($context == 'archive') $layout = 'single-small';
return $layout;
}

What other options can I assign to the $layout variable?

I just want to display the posts abstract and thumbnail to the left…