The thirteen skills a character can learn are:
Armor Use improves the resistances provided by armor, increasing damage mitigation. Resistances can also be affected by buffs and are capped at 50%. Armor Use is not required to equip armor.
Dirty Tricks gives you an arsenal of nasty tricks to use in a fight.
Dodge is used as the base value for Melee and Ranged Defense. The difference between your defensive ability (Melee/Ranged Defense) and your opponent's weapon skill (Melee/Pistol/Rifle) affects how likely you are to be critically hit.
Escape Artist helps you get out of rough situations. It also makes you harder to detect on the tactical map in PVP areas.
First Aid gives the player some abilities that heal others and is required to use items created with the Medicine and Mutagenics Skills.
Group Tactics allows the player to activate buffs on teammates during combat that can improve Accuracy, Stamina, and so on.
Heavy Weapons is your ability to equip and use Heavy Weapons. This skill does not become available til Level 40.
Melee allows players to inflict more damage in melee combat and use more effective melee weapons. The difference between your Melee and an opponent’s Melee Defense affects how much damage you do. It also determines your chances of scoring a critical hit.
Pistol allows players to inflict more damage with (and use more effective types of) pistols. The difference between your Pistol and an opponent’s Ranged Dense also affects how much damage you do. It also determines your chances of scoring a critical hit.
Power increases the damage you inflict with Melee, Pistol, and Rifle weapons.
Precision increases your chance to get a critical hit with Melee, Pistol, and Rifle weapons.
Rifle is similar to Pistol and Melee in that it affects the damage a character can do with the weapon and also allows him or her to equip increasingly more effective rifles. The difference between your Rifle skill and an opponent’s Ranged Defense affects how much damage you do. It also determines your chances of scoring a critical hit.
Social enables the character to finagle better deals from Merchants and also imbues them special abilities that allow them to conceal their faction alliance.