Again, you don't need to know how all this works to start playing, so don't let the amount of info put you off.
Survival stats will change all the time and... decide your survival.
Health/HP: Your most important stat. Health determines whether or not you are conscious, alive, and how well off you are. Many things will cause it to go down and many things will cause it to be recovered. Once it hits zero, you will pass out; at negative half your maximum health, you will die.
Fatigue: Reflects your overall tiredness. Decreases slowly over time and is used up whenever you try and use a skill. Recovered through rest/sleep and through the use of some drugs. As it gets lower, you will grow more and more tired and won't perform as well. If you let your fatigue go for too long, you'll pass out.
Hunger: Decreases over time, the speed of the decrease depends on the conditions you are living in at the time. Recovered by eating food. Once it hits zero, you will begin to take health damage until you eat something or die.
Thirst: Same as hunger, only it decreases much faster and is recovered by drinking acceptable liquids.
Radiation: Starts out at zero and increases whenever anything happens that would cause you to take radiation. Can be decreased over time and with special drugs and treatments. If kept at low levels for a long time, it can cause mutations. If it gets too high too fast, you will die. Unless they have special equipment that allows them to see it, players will not know their radiation levels past recieving messages like " You're feeling a bit sick".
Ability stats will set in the begining and increased only when you level up, they decide the values all other stats. They're also used in ability checks.
Strength/Str: Affects physical damage, carrying capacity, and body size. Used in checks that would involve feats of strength.
Perception/Per: Affects ranged accuracy and damage and stealth. Used in checks that would involve detecting things and searching.
Endurance/End: Affects damage resistance, body size, and the maximums of all survival stats. Used in checks that would involve enduring harsh conditions or taking big hits well.
Charisma/Cha: Affects appearance and generally how well you can trade. Used in checks that would involve communicating with NPCs.
Intelligence/Int: Affects stealth. Is used a lot in checks for checks.
Agility/Agi: Affects dodge rate, stealth, mobility, and body size. Used in checks that would involve mobility and avoiding things.
Luck/Luk: Has a small effect on everything. Determines random encounters, whether they will be or bad or happen at all
Used in checks that would involve you getting lucky.
Yeah, I jacked the fallout series' s SPECIAL. Sue me.
Body size: Increases with Str/End, decreases with Agi. Determines how big your character is and effects a lot of things. Big characters will be more intimidating to NPCs, get HP and resistance boosts, and can take more radiation, but will require more food/water to survive and take penalties to stealth and mobility. Small characters require less food/water, can fit in cramped spaces, and get boosts to stealth and mobility, but are less intimidating to NPCs, can get knocked around easier, and take less radiation. If you are too big or too small, you will take a penalty to appearance.
Appearance: The higher it is, the more attractive NPCs will consider you. I think the benefits to that are obvious.
Stealth: Used in checks that would involve sneaking.
Mobility: Determines how much ground you can cover in a turn and who strikes first in a combat turn. When moving in a group, the mobility of the slowest person is used.
What is a "check"?
That is when I make a dice roll using one of your stats.