Say you have a Post and you have different types of information (in a custom field or something) but you don’t want to have it all on the same page.
You can split this information out into different endpoints, something like /post-slug/details where /post-slug would general information and the /details would provide more in depth information on that post.
You can also use a different template to present your post based on endpoint. A /print endpoint for a post can load a printer-friendly version of your post without a header/footer/sidebar, or it could have a simpler design.