it give a param for description in array of the function to register widget:
register_sidebar()
Example can you see on this post or this code.
if ( function_exists('register_sidebar') ) {
register_sidebar(array(
'name' => 'My Lorem Ipsum Sidebar',
'description' => __('Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt explicabo.', 'your_textdomain'),
'before_widget' => '<li id="%1$s" class="widget %2$s">',
'after_widget' => '</li>',
'before_title' => '<h2 class="widgettitle">',
'after_title' => '</h2>',
));
}