These numbers identify a place holder for the content of that page.

The numbers at the end of the post address (URL) are optional.

For example ?p=694

We recommend including them because it ensures that the link will go to the correct page even if changes are made to the post address (URL) in the future. 

ADVANCED FEATURE: Later, when you have full control of the content and you want to make changes to that page, anyone with a link you provided earlier will still arrive at your custom page, if you leave these numbers when sharing the links.