Game concept
Ecclesiastical Estate
The game also links it as Ecclesiastical Estates, Cathedral Complex, Cathedral Complexes.
From the game's encyclopedia
An Ecclesiastical Estate — or Cathedral Complex — is a type of Domicile attached to a Clerical Title, representing the intimate landholdings of an Archbishop and their see. Lesser Clergy in an Ecclesiastical must rise to such a Title before they are granted one.
Ecclesiastical Estate Buildings may be constructed here to expand the holder's wealth, Piety, and Spiritual Fulfillment. The Ecclesiastical Estate does not change location and will be inherited by the next title Holder.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Ecclesiastical Estate is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "An Ecclesiastical Estate — or Cathedral Complex — is a type of Domicile attached to a Clerical Title, representing the intimate landholdings of an Archbishop and their see." It is part of Faith. The game also links it as Ecclesiastical Estates, Cathedral Complex and Cathedral Complexes. Patch 1.20.1.2, from game/common/game_concepts/pam_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/pam_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.