Usage of system_settings_form() function

We can store the entered field values by default, if we use the form variables as variable names,

function custom_settings() {

$form['disclaimer_content'] = array(

           '#type' => 'textarea',

           '#required' => True,

           '#title' => t('Disclaimer Content'),

           '#default_value' => variable_get('disclaimer_content',''),

           '#description' =>  t('Enter Disclaimer content.'),

);

return system_settings_form($form);

}