Wikia

A knowledge is a single activatable ability gained from skills or mutations, or a set of recipes. Each knowledge must be learned separately and requires levels in various skills. For example, learning Light Rifle, a Ballistics knowledge, requires a Ballistics of 75. It teaches you how to make Light Rifle Barrels, Light Rifle Actions, and Light Rifle Bodies, and how to combine these parts into a number of different rifles. If characters max out their respective skills, they can learn knowledges ten levels higher than their level. So if Light Rifle is a 25th level knowledge, a character could learn it at level 15 if they max out their Ballistics skill (and thus their Intelligence and Perception attributes). NPC opponents generally drop items equal to or below their level; thus crafters are the best source of equipment, since they can make things above their level.

Knowledges are categories of tradeskills, mutations, abilities, or other information tied to a character and used by the developers for managing actions in game.

Tradeskill Knowledge Categories:

Mutation Knowledge Categories:

Ability Knowledge Categories:

By default to see one's list of currently known knowledge one use the Alt-K key combination. One may see many knowledges prefaced with "old_" or "Old_"; these knowledges are primarily disabled or no longer used due to updates to the game.