This entry in the slice editor tells that this slice has some special purpose in the engine, such as being the slice representing an NPC. It's informative only; you can't change anything here.

For an NPC, its ID and reference numbers are shown.

For a hero, the caterpillar rank, hero ID and name are shown.

For the root slice of a slice collection this shows the Collection ID and name. (There are no script commands to get these.)