Most common wordpress functions
How to load WordPress template directory, WordPress home link, WordPress get author id by post, WordPress get author meta i.e display name
<?php
// wp home link
echo get_home_url();
//How to load wordpress template directory
echo get_template_directory_uri();
// or
bloginfo('template_url');
//get author id by post
get_post_field( 'post_author', get_the_ID());
//get author meta i.e display name
get_the_author_meta( 'display_name', $authorID );
?>