How can I define the output of shortcode attribute value?

According to Codex:

    
function shortcode_function_name( $atts ) {
   $atts = shortcode_atts( array(
      'attr1' => '',
   ), $atts, 'your-shortcode-name' );

   return '<div id="'.$atts['attr1'].'">Your Predefined Content</div>';
}
add_shortcode( 'your-shortcode-name', 'shortcode_function_name' );
    

Adding [your-shortcode-name attr1="Value1"] to the content of any post/page will give the following output <div id="Value1">Your Predefined Content</div>.

Adding [your-shortcode-name attr1="Value1"] to the content of any post/page will give the following output <div id="Value1">Your Predefined Content</div>.

etc…

And you can deep by adding the predefined content inside the shortcode, this way you can always change the predefined content inside the shortcode as well.

Hope it helps!