Game concept
Activity
The game also links it as Activities.
From the game's encyclopedia
An Activity is a special occasion hosted for a specific purpose, such as going on a Hunt to relieve Stress.
The Host holds the Activity in a specific Location, which affects it in various ways, and everyone who attends must Travel there.
Every attending Character interacts with each other by setting an Intent, which they try to pursue during the Activity.
A regular Activity such as a Feast or a Hunt are smaller and less impressive than Grand Activities.
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.
Activity is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "An Activity is a special occasion hosted for a specific purpose, such as going on a Hunt to relieve Stress." It covers Activity Option, Activity Type, Passive, Active, Activity Phase and 19 more. The game also links it as Activities. 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.