wordpress functions and explainings

function_widget_counter.php

<?php
// register sidebar widgets
function iatmul_widgets_init() {
	// footer widgets
	$footer_sidebar_number = 3; //Number of footer sidebars
	
	for( $i=1; $i <= $footer_sidebar_number; $i++ ) {
		register_sidebar( array(
			'name'          => sprintf( __( 'Footer Area %d', 'iatmul' ), $i ),
			'id'            => sprintf( 'footer-%d', $i ),
			'before_widget' => '<section id="%1$s" class="widget %2$s">',
			'after_widget'  => '</section>',
			'before_title'  => '<h4 class="widget-title">',
			'after_title'   => '</h4>',
			'description'	=> sprintf( __( 'Footer %d widget area.', 'iatmul' ), $i ),
		) );
	}
}
add_action( 'widgets_init', 'iatmul_widgets_init' );

latest_posts.php

<section>
  
  <?php 
  // more info on https://developer.wordpress.org/reference/classes/wp_query/
  // get the latest 3 posts, but withour the posts taged with 'sticky_posts'
    $args = array(
      'post_type' => 'post',
      'posts_per_page' => '3',
      'post__not_in' => get_option("sticky_posts")
    );
  
    $latest_posts = new WP_Query($args);
  
      if ( $latest_posts->have_posts() ) : while ( $latest_posts->have_posts() ) : $latest_posts->the_post(); ?>
        <?php get_template_part( 'template-parts/content' ); ?>
        <?php endwhile; else : ?>
          <?php get_template_part( 'template-parts/content', 'none' ); ?>
        <?php endif; wp_reset_postdata(); ?>

</section>

post_by_id.php

<?php

    $post   = get_post( 1875 ); // to get one single post or page by its ID (1875 in example)
    $output =  apply_filters( 'the_content', $post->post_content );
    echo $output;

?>

the_loop.php

<?php 
if ( have_posts() ) : // are there any posts or pages???

                the_archive_title( '<h1 class="page-title">', '</h1>' );

                // Start the loop.
                while ( have_posts() ) : // count every post or page you find

                    the_post(); // for all the metadata of the posts and pages
                    
                        ?><a href="<?php the_permalink(); ?>"><?php the_title( '<h3>', '</h3>' ); ?></a><?php // the post or page title with link to post or page
                        the_post_thumbnail(); // show post thumbnail
                        the_content(); // show full post or page content
                        the_content('Read the rest of this entry &raquo;'); // the content with readmore link
                        the_author(); // show the author
                        the_date( 'd-m-Y' ); // show the post date (day, mounth, year)
                        the_category(); // show the category the post belong to
                        the_meta(); // show meta data of the post
                        the_tags(); // show the post tags
                        next_posts_link( 'Older Entries', $the_query->max_num_pages ); // the next post
                        previous_posts_link( 'Newer Entries' ); // the previous post

                endwhile;

                the_posts_pagination(); // a pagination of the posts sites

else : // when there are no posts or pages show:
    _e("Sorry, but you are looking for something that isn't here."); // show this sentence, if there are no posts
endif;
?>