Strength is brute physical strength. High strength is beneficial for warriors. It modifies health, melee damage, and maximum carry weight.
Perception is the ability to see, hear, touch, and notice the unusual. High perception is essential for snipers. Modifies: ranged combat parameters and burst.
Endurance – stamina and physical strength. A character with high endurance will survive where others cannot. It modifies health, poison and radiation resistance, healing speed, and increases health with each level.
Charisma is attractiveness and charm. High charisma is beneficial for characters who want to persuade people with words. It affects NPC reactions and barter prices.
Intelligence – knowledge, wisdom, and the ability to think quickly. High intelligence is important for all characters. It modifies the number of skill points per level, dialogue options, and many skills.
Agility – coordination and the ability to move effectively. High agility is important for all characters. It affects: action points, armor class, turn order, and many skills.
Luck – Fate. Karma. A very high level of luck affects a character somehow. Events and situations depend on how lucky (or unlucky) your character is.
