Game concept
Estate
The game also links it as Estates, Family Estate, Family Estates.
From the game's encyclopedia
An Estate is a type of Domicile held by the House Head of notable Noble Families within Administrative Realms. They represent private landholdings untied to any particular Landed Title.
Estate Buildings may be constructed here to expand the family's wealth and Influence, and the Estate will be inherited by future generations.
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.
Estate is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "An Estate is a type of Domicile held by the House Head of notable Noble Families within Administrative Realms." It is part of Domicile. The game also links it as Estates, Family Estate and Family Estates. Patch 1.20.1.2, from game/common/game_concepts/07_ep3_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/07_ep3_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.