Sometimes it can be handy to have extra pages for a node (or any entity). For example: * To show different sets of information on separate pages for a single product, page, or thing. * So you can set different access requirements on each page for a node. * You want to block access to the ordinary route (e.g. node/123 and its aliased equivalent) for some reason, but you still want some other page to...
UPDATE: The Extra Field and Extra Field Settings Provider modules facilitate doing this sort of thing in Drupal 8. Read on for older Drupal sites, and for the concepts behind this. We often want to add things to the content of a node or any other entity in Drupal 7 using hook_node_view(), hook_node_view_alter() or a similar hook in a custom module. This could be anything from a custom social media link, a field rendered in...
We've been using Display Suite with Node displays on one of our latest sites. It was an experiment, and possibly not something we'll do again - DS offers some great functionality with build modes and ways to re-arrange fields and all sorts on nodes, but since we end up theming most nodes quite a lot anyway, it's not worth the extra hassle that Display Suite can add when you want to change the theming on...