Look at this site, here's an example of one of their links, they all have numbers at the end. What are they for and how do you do that? It can't be done manually is it? http://screenrant.com/zack-snyder-sucker-punch-superman-kofi-108001/
If you're talking about wordpress, then it denotes the post-id which is a unique id generated by wordpress for every single post/page. Anyways if it is some other platform also, it will usually denote the post-id. You can do this in Wordpress by changing the permalink settings to "custom" and put "%postname%-%post_id%" in the text field. There are several other tags available which can be used in the url. Check the Official Wordpress documentation for more reference below. http://codex.wordpress.org/Using_Permalinks