php - Wordpress basics

one text

Firstly, I'm a total beginner in this business but I decided to learn some php and now I'm trying to follow wordpress course .. which is by the way 5 years old. Anyway, I did the following code and it worked fine but vs code editor is saying that I am trying to use unknown function PHP(PHP0417).

The code is like this and according to vscode have_posts(), the_title(), the_content() is unknown function

Is the course outdated or what is going on?

<?php 

    while(have_posts( )) {
        the_post(); ?>
        <h2><a href="<?php the_permalink(); ?>"><?php the_title();?></a></h2>
        <?php the_content();?>
        <hr>
    <?php }
    
?>