Specifics: This feat grants the knowledge to make effective use of light armor. Characters without this feat cannot equip light armor.
Use: Automatic. All classes except wizards, sorcerers, monks, arcane tricksters, divine champions, Neverwinter Nine, Red dragon disciples, Red Wizards, Arcane Scholars of Candlekeep, and Sacred fists have this feat for free.
DnD 3.5 comparisonEdit
Characters could wear armor without the appropriate proficiency, but suffered the armor check penalty on attack rolls and on all Strength-based and Dexterity-based ability skill checks. Naturally one didn't suffer a penalty to spellcraft or knowledge skils from wearing armor.