Skills
As opposed to Attributes, which are measures of a person that all beings possess, Skills represent specializations that are not part of the quintessence of a character. As such, Skills may have zero points attributed to them.
Certain actions are available only to characters that have at least a certain number of skill points spent in a Skill - for example, labor at a construction site requires at least 1 Engineering skill point, while healing without a medpac requires at least 5 Medicine skill points. Furthermore, certain actions are available only to characters that have at least a certain number of skill points spent in a combination of skills - for example, building an Orbital Cannon requires at least 5 Engineering skill points and 5 Tactics skill points.
Available skills
Tactics
Tacticians are essentially battlefield specialists. They are able to set and recover mines (potentially damaging enemies that enter the minefield), and they are able to destroy buildings using special mines. Tacticians also receive a bonus during Orbital Bombardment missions.
Stealth
Stealthy characters are able to sneak about unseen, enabling certain missions such as Breaking and Entering and Infiltrating Enemy Lines. Characters with high enough Stealth ratings are invisible to characters without enough Awareness.
Awareness
Awareness is a sort of counter to Stealth. Awareness is used to spot characters hidden by Stealth and also to spot easy-to-miss items like mines. This skill enables missions such as Guard Duty.
Diplomacy
Diplomacy is a sister skill to Charisma. Diplomacy is used in interactions with NPCs and during character- and politically-oriented missions, such as Question the Locals and Official Negotiations.
Engineering
Engineering represents the ability of a character to build items and buildings. Crafting regular items doesn't require Engineering skill (although it does provide a bonus), but building construction does. Engineers are able to repair ships without visiting a shipyard and repair droids without repair kits.
Security
Security represents a character's knowledge of both electronic and physical security. Characters with security skills are able to more effectively hold other characters prisoner. Security enables certain missions, such as rescuing a character being imprisoned, and grants bonuses to other missions such as Breaking and Entering.
Medicine
Medicine represents a character's ability to treat injuries. Characters with high enough skill in Medicine have access to certain missions, such as healing a character without a medpac or Battlefield Medic. Medicine skills also make medpacs more effective.
Piloting
Piloting represents a character's ability to fly ships. Piloting opens space-oriented missions, such as Explore Deep Space, Bombing Run (in fighters), Orbital Bombardment (in cruisers and capital ships), and Run the Blockade.
Teras Kasi
Teras Kasi is an ancient martial art. Teras Kasi practitioners gain attack bonuses when wielding melee weapons (or no weapon at all), and they gain bonuses to Fortitude saves against melee attacks. Because of the mastery over self a Teras Kasi master has, Teras Kasi also grants small bonuses to seemingly unrelated activities, such as Will saves and Awareness checks.
Skill Proclivity
A user's raw skill point value doesn't tell the whole story of how good a character is in a particular skill. For example, a character with Security may be very good at picking locks, but very poor at hacking security systems. This is difficult to articulate using skill points alone, so a separate system is needed to demonstrate this: Skill Proclivity.
Each time a character uses a skill successfully on a task or mission, their proclivity with that skill goes up a small amount. Skill Proclivity represents a bonus to a particular skill, demonstrating something akin to practice. The relationship between skill level and proclivity can be thought of like this: Skill level represents the breadth of a character's knowledge in a skill, while their proclivity represents the depth of a character's knowledge in a skill. A character may have a high proclivity in Security, granting a large Security bonus, but still only have a small real skill level in Security. This indicates that a character doesn't know much about Security in general, but they are still very good at what they do know.
The functionality of Skill Proclivity is clear when one considers the fact that certain tasks and missions require a certain level of skill - Proclivity allows a character to be well-practiced at a skill without implying a breadth of knowledge. Characters with a Security skill of 1 can attempt the Breaking and Entering mission, but characters require a Security skill of 5 to attempt to slice a security system. However, it doesn't logically hold that a character with a Security skill of 1 should necessarily have trouble with Breaking and Entering - that only means that the character doesn't know much about Security. That character can still be quite talented within the limited range of their knowledge, and this talent within their knowledge is represented by their Proclivity.