How you can retrieve the course title from a publish ID.

May be the following a optimum way, or perhaps is there any simpler method.....

$category = get_the_category($post_id);
$cat_name = $category->cat_name;

I am unsure of what you are asking but when you're searching for shorter syntax:

$cat_name= get_the_category($post_id)->cat_name;

If you are just attempting to print a listing of groups owned by a publish, use...

the_category( $separator = '', $parents='', $post_id = false ) 

which echoes out links, or

get_the_category_list( $separator = '', $parents='', $post_id = false )

which returns a string with links.

If you would like the publish groups as a range of objects use get_the_category( $id = false ).

The publish ID is optional: whether it's overlooked the functions assume that you're speaking about global $post. If you are informed this works, otherwise you will need to pass the publish ID.

Regardless, a publish can fit in with several groups, not merely one, despite the fact that the function names imply otherwise.

Each one of these functions live in wp-includes/category-template.php.