Game concept
Activity Phase
The game also links it as Activity Phases.
From the game's encyclopedia
An action phase of an activity such as a Contest in a Grand Tournament, Stop on a Tour, or destination of a Pilgrimage during which events occur.
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 Phase is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "An action phase of an activity such as a Contest in a Grand Tournament, Stop on a Tour, or destination of a Pilgrimage during which events occur." It is part of Activity. It covers Activity Phase Action. The game also links it as Activity Phases. 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.