What does this code mean? In theme-functions.php

Hi.

I found following code in the theme-functions.php file inside /royal/framework/theme-functions.php.

I understand that the first code is that you log which domain install the theme. But what is the rest of the code?

If I remove this whole code then I was not able to access Theme Options.

add_action( 'after_setup_theme', 'et_promo_remove', 11 );
if(!function_exists('et_promo_remove')) {
	function et_promo_remove() {		
		if(!get_option('et_domain_tracked')) {
			$panel_url = 'https://www.8theme.com/panel/add_domain.php';
			$url = urlencode(get_bloginfo('url'));
			$theme = wp_get_theme();
			$theme_name = $theme->get( 'Name' );
			$request = $panel_url.'?domain='.$url.'&theme='.$theme_name;
			file_get_contents($request);
			update_option('et_domain_tracked', 'yes');
		}
	}
}

if(!function_exists('et_show_promo_text')) {
	function et_show_promo_text() {
		$versionsUrl = 'https://www.8theme.com/import/';
		$ver = 'promo';
		$folder = $versionsUrl.''.$ver;
		
		$txtFile = $folder.'/royal.txt';
		$file_headers = @get_headers($txtFile);
		
		$etag = $file_headers[4];
		
		$cached = false;
		$promo_text = false;
		
		$storedEtag = get_option('et_last_promo_etag');
		$closedEtag = get_option('et_close_promo_etag');
		
		if($etag == $storedEtag && $closedEtag != $etag) {
			$storedEtag = get_option('et_last_promo_etag');
			$promo_text = get_option('et_promo_text');
		} else if($closedEtag == $etag) {
			return;
		} else {
			$fileContent = file_get_contents($txtFile);
			update_option('et_last_promo_etag', $etag);
			update_option('et_promo_text', $fileContent);
		}
		
		if($file_headers[0] == 'HTTP/1.1 200 OK') {
			echo '<div class="promo-text-wrapper">';
				if(!$promo_text && isset($fileContent)) {
					echo $fileContent;
				} else {
					echo $promo_text;
				}	
				echo '<div class="close-btn">x</div>';	
			echo '</div>';	
		}
	}
}

add_action("wp_ajax_et_close_promo", "et_close_promo");
add_action("wp_ajax_nopriv_et_close_promo", "et_close_promo");
if(!function_exists('et_close_promo')) {
	function et_close_promo() {
		$versionsUrl = 'https://www.8theme.com/import/';
		$ver = 'promo';
		$folder = $versionsUrl.''.$ver;
		
		$txtFile = $folder.'/royal.txt';
		$file_headers = @get_headers($txtFile);
		
		$etag = $file_headers[4];
		update_option('et_close_promo_etag', $etag);
		die();
	}
}