Game concept
Levies
The game also links it as Levy.
From the game's encyclopedia
The bulk of most Armies is made up of Levies.
Each Holding provides a set number of Levies to their Holder. Vassals in turn provide a part of their Levies to their Liege.
Levies are made up of mostly poorly-armed fighters (peasant militias, ruffians, local sellswords, destitute nobles, minor landowners, etc.) and are considered their own unit type.
A Levy has 10 Damage and 10 Toughness. The other type of Soldiers in the game are Men-at-Arms — expensive trained professionals.
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.
Levies is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "The bulk of most Armies is made up of Levies." It is part of Soldiers. The game also links it as Levy. 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.