understanding the return .

understanding the return .

what does the return statement really say ? 

  2.   $( "li" ).click(function (e){
  3.   $(this).filter(function( index ) {
  4.     return $( "strong", this ).length === 1;
  5.   })
  6.     .addClass('me');
  7. });

does it read as the following ?? 

if ($( "strong", this ).length === 1){
      return true ;
}else {
     return false ; 
}

also why the "index" parameter on the filter function ??