WordPress at a glance
function is not described

wp_create_term() WP 2.8.0

Add a new term to the database if it does not already exist.

No Hooks.

Return

Array/WP_Error.

Usage

wp_create_term( $tag_name, $taxonomy );
$tag_name(int/string) (required)
$taxonomy(string)
The taxonomy for which to retrieve terms.
Default: 'post_tag'

Code of wp create term: wp-admin/includes/taxonomy.php VER 5.0.3

<?php
function wp_create_term($tag_name, $taxonomy = 'post_tag') {
	if ( $id = term_exists($tag_name, $taxonomy) )
		return $id;

	return wp_insert_term($tag_name, $taxonomy);
}