Jerusalem in CK3 is called the Kingdom of Jerusalem once it exists, and in 1066 itself it is just the province/county of Jerusalem in the Levant, not yet a crusader kingdom.

In game terms

  • 1066 start: Jerusalem is not a crusader kingdom yet; the historical crusader state only appears after the First Crusade in 1099.
  • After a successful crusade: it becomes the Kingdom of Jerusalem.

Why the name matters

If you were asking about the title you can create or win through crusades, that title is Kingdom of Jerusalem.

If you meant the place on the map at the 1066 start, it’s simply Jerusalem as a county/province in the region that later becomes the crusader kingdom.