Game concept
Learning Skill
The game also links it as Learning.
From the game's encyclopedia
Learning is a Skill measuring a Character's literacy and wisdom. The Learning Skill of a Ruler affects the cost of increasing Crown Authority, and also yields an amount of monthly Piety.
Characters with high Learning can be expected to have extensive knowledge of all common scholarly endeavors, including theology, philosophy, language and mathematics.
The corresponding Lifestyle is the Learning Lifestyle.
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.
Learning Skill is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Learning is a Skill measuring a Character's literacy and wisdom." It is part of Skills. The game also links it as Learning. 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.