Publish Related Items are:

Clone references – items that are clones of the selected item.

Media references – media items that are related to the selected item.

Alias references – items that are aliases of the selected item.

This is lifted from the Sitecore Doc site its near the end. Here is the link [Publish an item to your website][1]

Hope this helps. [1]: https://doc.sitecore.net/sitecore_experience_platform/content_authoring/publishing/publish_an_item_to_your_website

Publish Related Items are:

Clone references – items that are clones of the selected item.

Media references – media items that are related to the selected item.

Alias references – items that are aliases of the selected item.

This is lifted from the Sitecore Doc site its near the end. Here is the link Publish an item to your website

Hope this helps.