WordPress at a glance
function is not described

get_default_feed() WP 2.5.0

Retrieve the default feed.

The default feed is 'rss2', unless a plugin changes it through the 'default_feed' filter.

Hooks in function
Return

String. Default feed, or for example 'rss2', 'atom', etc.

Usage

get_default_feed();

Code of get default feed: wp-includes/feed.php WP 5.2.2

<?php
function get_default_feed() {
	/**
	 * Filters the default feed type.
	 *
	 * @since 2.5.0
	 *
	 * @param string $feed_type Type of default feed. Possible values include 'rss2', 'atom'.
	 *                          Default 'rss2'.
	 */
	$default_feed = apply_filters( 'default_feed', 'rss2' );
	return 'rss' == $default_feed ? 'rss2' : $default_feed;
}