A permanent link to an item (a blog post, an attachment, ...). The default structure is "?p=123", but WordPress can handle "pretty permalinks" and will rewrite them internally to the former version. If you have a question about special rewrite structures you should use the [url-rewriting] tag.
I understand there are 2 different types when it comes to a custom post type: -page -post. Where page supports child pages, and post does not. However, when i try to make a child page with only ...