- the ability to use one's knowledge effectively and readily in execution or performance
- dexterity or coordination especially in the execution of learned physical tasks
- a learned power of doing something competently; a developed aptitude or ability
Skill is not given to us by the game. Skill is learned and grown from experience; it is a willingness to learn, an ability to learn, and applying it directly to our play. It's your adaptability and your mental "processing power." Greater skill at one task will lead to quicker learning of a similar task, and this is why skill is so important in progression raiding (any raid where you aren't overgearing the content) and PvP.
Things we gain skill in include use of our own computer (your keyboard and mouse, your direct link into controlling the game), ability/spell selection, reaction speed, and awareness of what things are or might be "bad" (be it a boss ability, environmental effect, or even a game mechanic like pulling aggro or going out of healing range). The speed and accuracy of these things are what make a skilled player... and they are born out of the ability to learn, mental quickness, and experience.
Skill is NOT:
I have known players who have failed to improve after being given all the "right" tools. On the flip side, I have known skilled players who didn't use many of these tools at all (we just about all use some mods!). Skill and tools help each other to make a better player, but they are not the same thing.
How do they relate?
In my rough opinion,
|Skill + Tools = Player Performance|
Skill, or the ability to learn from experience while adapting it to a new situation, is very important. Various tools(when used correctly) add to your situational awareness and aid in processing information, such as perusing logs or comparing gear or knowing what stats you should focus on to what caps; the stats on the gear itself will aid in your overall output and survivability.
A player with a lot of appropriately-used tools can make up for some failing of skill; likewise, a player with a lot of skill can make up for some failing of tools. A player who makes great use of tools while being highly skilled makes for an exceptional player. Though it's not always fair to count on one's luck with gear drops in the game as a measure of their ability as a player, you cannot deny that a person with a legendary weapon should have an edge over someone with a weapon from a heroic 5-man.
Not all tools are accurate or appropriate, either. In a simple example, we could say "Wow, that guy has a i-level 9,000 shirt! He must be AWESOME!" while the shirt is all +spellpower and he's a warrior. While that is unlikely to ever happen, there are some more realistic examples: like sims that don't take into account your own raid composition, or BiS lists that aren't made for a WotLK 10-strict itemization, or suggested rotations that assume you'll have full raid buffs, or that someone else will take care of a debuff that you would otherwise need to apply (mangle/trauma, IFF/misery, totem juggling, etc). Or situations where you could spike the meters through the roof by AoEing on a pack of adds while some other mob should be CC'd or interrupted or single-target-bursted down before it wipes the raid: because you topped meters, you think you did everything right.
This relationship is why we often see people mistakenly equating various tools to skill: they ultimately both impact a player's overall performance. For example (allow me to beat a dead horse for a paragraph), Gearscore is often used as a limit on invites to pug raids because it's a measurable component of the overall performance you would expect from that player. It does not measure actual player skill in the slightest, of course, but some players do like to imagine that it does. What Gearscore does allow is for a raid leader to ensure at least one crutch (being gear with a lot of raw stats) to lean on towards success in an otherwise unknown mash-up raid. Even if I don't like seeing people use Gearscore, I can't deny that gear does contribute in some amount to a raid's success: gear is specifically why we see WotLK 25-man guilds clearing through the lower-iLevel (and less itemized) 10-mans with relative ease. However, gear is just a tool (one that can be misused), and a player not having gear does not mean they can't make up for it with skill... just as a geared player may not necessarily be skilled.
Short of the long: if the guy with the legendary is dead in a fire cuz the internet dragon ate him for the fiftieth time, he's worthless against the raider in blues who is alive because he learned at level 12 that "fire=bad."
How would we measure Skill?
If we could provide a "skillscore," how would we do it? I imagine, for purposes of awareness, it would involve the statistics tracking: number of times you've died to cleave as a DPS/healer, or died in fire, or got hit by a death beam. It would need to be more particular, though: how many times you did these things when the raid was still mostly alive, as I know I use these insta-death mechanics to facilitate a quick wipe when we're resetting a boss for another try! Or whether the tank was still alive, as top-threat dps or healer is sure to die next after a tank goes down. You could measure reaction times by monitoring combat logs, especially in the case of healers or interrupts, or tanks swapping taunts or using protective cooldowns. It's possible with algorithms, but that's only a rough sketch that doesn't cover every possible thing that could happen in a raid, and whether it's that player's fault.
Some other aspects of skill are much harder to quantify: what about those times a tank decides to run LoS from healers? Or carries a cleave or whirlwind right over their squishy fellow raiders? Or how about spell selection--how do you measure that, when it needs to be adaptable from boss-to-boss, situation-to-situation, PvE to PvP, raid comp and spec and talents and lag all contributing to your choice? What about those times a player's just "off" that night, due to mood or lack of sleep or dehydration or family distractions, or a major need for a bio break in the middle of a 15-minute-long encounter, reducing their attentiveness?
How exactly do you measure the full extent of someone's ability to perform their job, without being able to measure their skill? All we can do is to play with a person and see how quickly they learn in a new situation: their adaptability, learning speed, and reaction times. It's not a quantitative measurement, but there is a definite qualitative bar you can place any given person on and say "yeah, she's pretty good," or "wow, that guy sucks," or even "HOLY CARPS we need to recruit that person NOW."
I spent some time, long ago, trying to help another player who was having a lot of trouble. They were very nice and willing to learn. I sent them all of my mods and macros. I helped them set them up over vent. I walked them through how I chose spells, how I wove my spells when healing, etc. Their gear was on par for the content, and was on par for the others they were healing with. They had a good computer and didn't have a high latency. They didn't die very often to "bad stuff;" they seemed situationally aware.
But they just didn't improve.
I worked with them for a long time. I still feel bad to this day that I never saw any increased performance out of them. All I could do was shrug and say "keep trying." As much as I liked them, I knew the only other possibility was that it had to be an issue of player skill. It was something difficult to pinpoint and quantify, but the result was clear: a poor healer.
Skill + Tools = Player Performance
Don't say gear = skill. Don't say mods or sims or spreadsheets = skill. Those are tools to help you in your growth and ability as a player. Skill, on the other hand, is your adaptability, your experience, your willingness to learn, and your mental reaction time all rolled up into one incredibly-difficult-to-quantify ball of "skill."
You can have a skilled player who doesn't make use of many tools, like spreadsheets or having great gear... just as you can have an unskilled player walking around with a Legendary and quoting EJ (and then dieing in a fire). When recruiting or even looking at a random person standing next to you at the inn, keep that in mind before judging their "skill."