WordPress at a glance
function is not described

previous_posts() WP 0.71

Displays or retrieves the previous posts page link.

No Hooks.

Return

String/null. The previous posts page link if $echo = false.

Usage

previous_posts( $echo );
$echo(true/false)
Whether to echo the link.
Default: true

Code of previous posts: wp-includes/link-template.php VER 5.0.3

<?php
function previous_posts( $echo = true ) {
	$output = esc_url( get_previous_posts_page_link() );

	if ( $echo )
		echo $output;
	else
		return $output;
}