Drupal 7, create tabs in hook_menu

scratch.txt

function social_links_menu() {
  $items['admin/config/system/social_links'] = array(
    'title' => 'social_links',
    'description' => 'Configure to fit clients needs',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('social_links_settings'),
    'access arguments' => array('administer site configuration'),
    'file' => 'social_links.admin.inc',
  );

  $items['admin/config/system/social_links/tab1'] = array(
    'title' => 'Tab 1',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10
  );

  $items['admin/config/system/social_links/tab2'] = array(
    'title' => 'Tab 2',
    'type' => MENU_LOCAL_TASK,
    'page callback' => 'some_callback',
    'access arguments' => array('some permission')
  );

  return $items;
}