A favicon is a little 16×16 pixel image that appears in your browser tab to the left of the web page description (or if using IE or safari, it appears to the left of the webpage url in the address bar). If you are unsure where this code should be placed, just do a quick search on Google, there are plenty of tutorials.
For a normal website, you can insert this snippet somewhere within the head tag:
<link rel="shortcut icon" href="/favicon.ico" />
For a WordPress website you can use the following which needs to be placed somewhere within your opening and closing head tags in the header.php file :
<link rel="shortcut icon" href="<?php bloginfo('stylesheet_directory'); ?><!--File Path-->favicon.ico" />
This will retrieve your favicon from your theme path (or child theme if you’re using that).
*Make sure you specify the file back correctly within the snippet.