What is [new]?

Working my way through a block of code that contains some elements I'm not familiar with. This will actually be a string of several questions so feel free to weigh in however and whenever you like.

Here's the code my button is triggering:

    $('#btn-add-user').on('click', function () {
        $(window).trigger('user-form-show', ['new']);
    });

I traced that to this (I'm only including a portion of the code):

$(document).ready(function(){

    $("#chk-user-active").on('change', function () {
        $('#user-active').val(this.checked);        
    });
  var $uModal = $('#modal-user-form'),
      $form = $('#user-form'),
      $passwordButton = $form.find('.btn-change-password').clone(),
      $passwordForm = $form.find('.password-template').clone().removeClass('d-none'),
      data = [],
      loadedUserId = '',
      passwordRegex = {
        upper: /[A-Z]{1,}/,
        lower: /[a-z]{1,}/,
        number: /[0-9]{1,}/,
        special: /[\!\@\#\$\%\^\&\*]{1,}/,
        total: /.{8,}/
      };

  $form.find('.field-phone').mask('000-000-0000');

  $form.find('.password-template').remove();

  $(window).on('user-form-show', function(e, userId, opts){
    // prep the modal
    $uModal.find('.loading').show();
    $uModal.find('.main').hide();

    // show the modal loading screen
    $.magnificPopup.open({
      alignTop: true,
      items: {
        src: $uModal, // can be a HTML string, jQuery object, or CSS selector
        type: 'inline'
      }
    });

    // clear the cached data
    data = {};

    // clear the form from any previous data
    clearForm();
           

    // load the data if a valid id is provided
    if (typeof userId != 'undefined' && userId != 'new') {
      loadFormData(userId);
    } else {
      // set the id for a new user
        loadedUserId = 'new';
        // load drag & drop members 
        teamDragula(userId);

        $form.find('#user-role').attr('data-user-id', loadedUserId);
      // force the password fields
      $form.find('.btn-change-password').replaceWith( $passwordForm.clone() );
      $form.find('.btn-cancel-password').closest('.col').remove();

      // show the form
      $uModal.find('.loading').hide();
      $uModal.find('.main').show();
    }
  });

Select allOpen in new window

My first question pertains to the syntax used to trigger the "user-form-show" function:  $(window).trigger('user-form-show', ['new']);

I looked up "window," so I understand that, but what is [new] and why is it in brackets?

That's Question #1!