What do you mean by item and end product?
The item is what you purchase from Envato Market. The end product is what you build with that item. For example, the item is a business card template; the end product is the finalized business card. The item is a button graphic; the end product is an app using the button graphic in the app's interface.
What does royalty free mean?
Royalty free means you just need to pay for rights to use the item once per end product. You don't need to pay additional or ongoing fees for each person who sees or uses it.