$shipping->quote() parameters: what are they for?

[katapofatico 8]

I never understood the meaning and purpose of the quote() function parameters on shipping.php class:

class shipping {
(...)
    function quote($method = '', $module = '') {

neither the sub-uses on shipping modules, for example:

class usps {

    function quote($method = '') {

Ok, in this example I can see using of $method parm:

if (($method == '' && in_array($type, $this->types)) || $method == $type) {
        if (strpos($type, "Flat Rate")) $type_flat = $type . ', subject to verification';
        else $type_flat = $type;
               $methods[] = array('id' => $type,
                               'title' => $type_flat,
                               'cost' => ($cost + MODULE_SHIPPING_USPS_HANDLING) * $shipping_num_boxes);
            }

But, excuse me, I can't imagine the meaning. Can anybody explain us what's the meaning and when is useful to use it?

 

Thanks a lot, seriously: your answer can alleviat a dude in my mind from several years ago!  (excuse my English) :D

Edited February 22, 2016 by katapofatico