How To Display Category list from Portfolio post type plugin?

FYI, the Portfolio Category in your website is called Custom Taxonomy.

You will need a function called get_terms() which takes two params are the taxonomy you will get and an array. It will return an array of terms. Just surf the codex about that. After get the terms, you can use a foreach loop to display your result.

Example code:

$terms = get_terms( 'portfilio_category', array(
    'hide_empty' => false
));

foreach ($terms as $term) {
    echo $term->name;
}