Solution for Portfolio Page not displaying "portfolio" type posts and featured images

Here is how I fixed it (not that I understand the replaced code):

1. Opened page-portfolio.php from downloaded project files under this video.

2. Compared it to my own page-portfolio.php (identical to the tutorial video).

3. Noticed Line 24 of downloaded project file: <?php get_template_part('content', 'portfolio'); ?>

4. Opened project file "content-portfolio.php". Here the php block with WP_Query (line 1-11) has extra code:

<?php 

  $num_posts = ( is_front_page() ) ? 4 : -1;

  $args = array(
    'post_type' => 'portfolio',
    'posts_per_page' => $num_posts
  );
  $query = new WP_Query( $args );

?>

my php block with WP_Query from following the tutorial had only

<?php

  $args = array(
    'post-type' => 'portfolio'
  );
  $query = new WP_Query( $args );

?>

I replaced my original WP_Query block with the one from "content-portfolio.php".

Now it works - the portfolio page is displaying "portfolio" posts and featured images.