This is sort of like asking an Earth-person to give an impromptu rundown of all the major subjects in science and technology. Haroun will give it a try anyways.
Social Skills are first and foremost Skills; anything that people can get better at with practice can become a Skill. In Haroun's own mind, there's no pre-existing sharp delineation between Skills that work by direct empathy versus Skills that work by reading facial microexpressions or whatever. Asking whether a reading Skill can be blocked by an opaquing or faking Skill doesn't help; an opaquing Skill could easily include subskills for controlling your facial microexpressions. Testing how readable Bella is might answer some of those questions, but of course that's exactly what they want to know. And in any case, 『Unique Skills』 are a big enough deal that one with a name like 『Inviolable Mind』 could easily turn out to interfere with reading facial microexpressions too if that was being done in a Skill-based way, just because.
The range of Social Skills isn't much narrower than the regular human range of Social Skills? Especially important or popular ones include Leadership, Bargaining, Dispute Resolution, 『Game Theory』, Lie Detection, Lying, and Seduction. If Bella finds herself wanting to sleep with a man she met only a few minutes earlier - assuming that kind of Skill even works on Bella - she should probably be even more suspicious than she otherwise would be. The fundamental weakness of Social Skills is that, as with any other Skill, improving at some procedure with practice doesn't mean that procedure is useful. To put it in Bella's terms, practicing Freudian psychotherapy and becoming extremely good at coming up with plausible interpretations of dreams isn't going to save you in the event that Freudianism is bullshit. Studying pickup artistry and becoming very good at 'negging' isn't going to help if this is a person who doesn't take well to being negged; you'll just become able to shoot off your own foot faster. Ultimately there's no such thing as a Skill for 'successful persuasion', there's only Skills that correspond to particular people's theories of how to persuade others, and whatever they ended up practicing based on their own observations and theories. Sure, some of them became good at it by external standards, and that's the basis on which people select which Skill-acquisition exercises to do and which Skill trees to go down. But you're still fundamentally getting what the other person practiced at based on their theories of what was working, not anything that's guaranteed to actually work.
If you want good Bargaining Skills, you'd better hang out with enough successful merchants that you can ask them what books they read and what exercises they did. But that process does get you a lot further than it would in Earth - you're much more likely to actually pick up the same Skill if you do the same exercises the successful merchant did.
What are the big Skill categories? Goodness, what a question. It depends on how you look at things. Melee could be divided (of course there'd be people who argue with you about the particular division) into physical close attack, physical defense, physical ranged, spellcasting for close attack, spellcasting for defense, spellcasting ranged, spellcasting battlefield control, spellcasting for support before the battle, spellcasting for recovery after the battle, alchemy used before and after the battle, and enchantments for supporting all of the above.
Crafting Skills... gosh, Haroun doesn't really know what sort of divisions would apply here. Going by which Guild sells the finished goods doesn't seem very fundamental; lots of finished goods require all kinds of different Crafting Skills as input. He could try for a division like 'Skills that work metal versus Skills that work plant products versus Skills that work everything else' but would there really be a point to that? What makes so many Crafting Skills be 2nd-tier if not 3rd-tier is the number of different processes you have to tie together to get the finished product. Maybe it's worth distinguishing enchantments on tools that help make more things, versus enchantments on the things themselves? Objects that require complicated individual enchantments will obviously tend to be much more expensive than objects that only require heavily enchanted tools to make; but even those would be cheap per-use by comparison with consumables like potions. That's one possible view of a big division in Crafting; the difference between consumables and reusables and tools. Is this helping at all? If you wanted to study how to craft daggers at Haroun's academy, they'd send you off to a dozen different courses for the first-tier Skills you'd need first, and those first-tier Skills would come from all over the place and be shared by a hundred other possible Crafting specialties.
All the Skills related to Farming are a major part of what makes the world go around, even if they don't figure as much in tales and legends. But of course that category includes some Crafting and Tamer and Social Skills; a farmer needs to know how to sharpen a plow, feed an ox, and sell the produce to a merchant.
Bella may get the impression, as she listens, that Haroun's world doesn't think in quite the same way about dividing knowledge into compartmentalized Subjects, the way a college's course catalog does on Earth. There are just thousands upon thousands of Skills, and all the 2nd-tier ones have multiple prerequisites, and that's their experienced ground reality for what kinds of knowledge depend on each other. Any attempt at categorizing knowledge more broadly is hard for them to take seriously because of all the Skills whose prerequisite lists will cross over whatever boundaries you care to name. The most natural division their society sees is the division between, say, a Close-Combat Adventurer and an Alchemical Florist. But those people are distinguished by their jobs, the kind of services they sell, not by their having studied only one particular kind of knowledge. They're both going to have the Bargaining Skill listed as something you should try to acquire if you're taking on that profession - though in neither case will it be a core Skill, a priority. You can get by without investing time in Bargaining yourself, if you lack talent and have a sufficiently trusted friend who is sufficiently good at it; though this is a proverbial way of courting disaster.
Some professions have specialties which happen to run on tightly interrelated Skill lists with lots of mutually reinforcing prerequisites. Haroun's term for this is, inevitably, translated in Bella's mind as a 'Class'.
Haroun wonders how Bella's world gets by without the ability to directly tell how much Skill people have acquired. How can anybody tell which academies are best? How do guilds distinguish masters from apprentices? Are there specialized guilds that do things like testing the cutting power of swords before they're sold? It seems like you'd have to invest a lot more effort in that sort of thing if there weren't guilds certifying that people have acquired all necessary Skills to their required levels. And wouldn't that tend to skew the incentives toward manufacturing goods with high immediate performance and less long-term durability? Do hospitals spend tons of time and paperwork measuring which healers get the best patient outcomes, and wouldn't that give healers an incentive to only accept patients with better prognoses? It's not like Bella's people can directly measure anyone's skill level at the trickier healing spells, and anytime a patient dies the healer could just claim they had an especially tricky case. How do you verify that educators actually have the Social Skills for Teaching, rather than just being good at persuading people to believe they understood something? How do you even figure out which Teaching Skills are the good ones - the ones that taught the greatest heroes - if there aren't any Skills? Why don't their academies just degenerate into a lot of people airily waving their hands and pretending to teach things while actually uttering nonsense? Bella's culture must have all kinds of fascinating adaptations to a reality where competence, fundamentally, cannot be measured except in special cases... he's drifting off the point again, isn't he. He might need to go to bed soon.
It's just hard for him to guess what aspects of his world Bella would find surprising! Skills operated by rituals and incantations? There are Skills like that for summoning/generating monsters that need Taming but then stick by your side until killed, though those take a lot of mana. There are also cheaper Skills that generate something like an illusion of a monster that's capable of wielding claws and doing other physical damage - though that's still well above Haroun's own mana and skill range. There are incantation-operated Skills for improving the accuracy of thrown daggers, and curing a disease that sounds like scurvy, and clipping toenails, and cleaning clothes, and helping fields absorb fertilizer, and changing trees to have prettier leaves. Nobody has ever developed a Skill that will change the color of the leaves in a new tree that grows from the old tree's seed, and some people get sort of mystical about that, talking about how the power of seeds to grow new life is a power beyond sapients to master, a power beyond 『Language』 even. Is any of this helping Bella at all?
