Brave and Faith are two hidden stats that significantly impact character performance. Brave affects the activation rate of Reaction abilities and the damage of certain physical attacks (e.g., Monk's Punch Art). Higher Brave is generally desirable for physical attackers.
Faith affects the power of magic spells (both yours and enemy's) and the success rate of status effects. Higher Faith is crucial for magic users but makes them more vulnerable to enemy magic. You can manipulate these stats using abilities like 'Cheer Up' (Squire) and 'Preach'/'Solution' (Orator). Be careful not to lower Brave or Faith too much, as units with extremely low stats will permanently leave your party.