Health - Your health
Armor - Armor of your vehicle
Clothes - Condition of your clothes. It reduces your damage. You'll catch a cold if it's too low. 

Bobby Pins - Used to pick locks
Stimulants - Heal your health. Can be used in combat
Medkits - Heal your health greatly. Cannot be used in combat
Antibiotics - Cure infections
Repair Kits - Repair your vehicle's armor
Flashbangs - Used to stun enemies to run away in combat
Spare Clothes - Used to change clothes
Fuel Tanks - Used to refuel your vehicle

Guns - affects your aim accuracy and damage you give
Repair - affects your efficiency of Repair Kits
Sneak - affects your probability of successful sneaking and escape
Lockpick - affects your lockpicking ability
Survival - affects your effectiveness of food and water
Speech - affects your success rate of persuasion and intimidation
Barter - affects purchase prices of items
    Some skills affect certain options in some events

Fully Automatic - Enables you to shoot faster and continuously
Floating Module - Enables you to cross rivers safely
Booster - Enables you to travel faster (with increased fuel consumption)
Motion Tracker - Detects enemies and prevents ambush
Disinfector - Prevents illnesses caused by contaminated water
Stabilizer - Reduces your gun's recoil
Ballistic Armor - Reduces your vehicle's armor damage taken