Game concept
Objectives
From the game's encyclopedia
Certain parts of an enemy Realm (usually the Realm Capital and the Holdings in the War Target region of a War) are considered Objectives. By Occupying Objectives, you start gaining 'ticking' War Score.
For the Defender, War Score starts to tick up (after an initial period of time) if the Attacking side can be prevented from Occupying any Objectives.
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.
Objectives is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Certain parts of an enemy Realm (usually the Realm Capital and the Holdings in the War Target region of a War) are considered Objectives." Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.