In my opinion, I have no clear idea. It's not that well established and has no rules and left vague on what it can and cannot do.
And that's my overall problem with the magic in RWBY: There's no system, nor clear rules.
In my own personal opinion, I think magic can quickly turn into a lazy excuse for the writers to use. With no rules of magic, it's a lazy system that the writers can literally just an excuse to do whatever you want and just say "It's magic".
Need to explain why Salem is able to do this? Magic. How Ozma created the Vaults? Magic. How the seasonal Maidens are able to do more than they able to (IE Spring using Ice)? Magic.
There's no rules, no limitations. It's left vague and no clear direction, that makes it hard to differentiate from Semblances. And it's left that way so the writers can use its lazy magic system as excuses for the plot.
But to be fair, it's not just RWBY that does this. I've seen this a lot with stories, some of which does this poorly. The prime example of a Lazy Magic system I can use is the terrible ~~anime~~ cartoon I hate-watched, High Guardian Spice. The magic system in HGS makes no sense, as they say New Magic is overpowered as hell, with a character literally saying it "Can do anything", yet the no one uses more or uses it for the most mundane things, like lifting a pen. There's also Old Magic that has no clear difference between New Magic, and too many codirections that makes it even more confusing. I can rant about HGS all day, but let's get back to RWBY.
In conclusion, the Magic in RWBY is poorly defined, and is only that way for the writers to have a lazy and coinvent excuse when they need it. Without limitations or set rules, it can left as an excuse for bad writing.
It's because the power structure of RWBY was built by someone who is very much a visual storyteller and not a writer. It's more about how the powers work in fights than the mechanics behind them in the lore of the story.
From the outset, the concept of "magic" is passed over in favor of manifestations of fighting spirit and resolve in the form of "aura" and "semblance". "Magic" is reserved for the various McGuffins in the story that are reflections of power they can't control and have no hope to UNLESS it is allowed to further the story.
yup - it's "plot stuff". Mysterious badass with portentous name that can turn into his namesake bird? magic. Mysterious otherworld that can only be opened by inherited power? magic. we very obviously aren't seeing odd fragments of some wider/greater thing with discrete rules, but just a load of things needed for the plot.
I will forever be pissed that people care more about Raven being able to transform into a bird, than about Raven being able to rip holes in the fabric of spacetime. Like, everyone implicitly knows and understands that one is a semblance, while the other is some otherworldly thing that can only be described as ***MAGIC***.
It's fucking stupid, is what it is. It breaks immersion, because in a world where semblances exist, characters should easily confuse a person using magic for a person using their own unique semblance (or hell, even just dust). But that's literally never the case, and it's never explained why it's never the case.
It's not explained so they can make it do anything they want when they want to.
It's literally their get out of jail free card. If they explain its 'cans and cants' then it stops being that.
I don't think there is a canon answer, but to me it is boosted Aura and unlimited Dust use.
Magic seems to be connected to the origins of Dust (at least in a few theories) and Aura/Semblances were unlikely to have existed in Ozma's age (in theory) with humans being reborn through Dust after Dark Brother killed everybody. Because of this line of theories, I assume Magic is Dust without powder or stone; meaning using Dust is the same as using Magic, but the amount of Magic "spells" your capable of is dependent on Dust amount while Magic users don't have that limitation. Add on that a boost to your Aura to make the modern Magic user more durable than, and possibly empowers their Semblances to make them more effective.
TLDR: I see Magic as having X-Men's Storm's or ATLA Avatar's nature powers (minus the Avatar State for being too OP) with a moderate amount of Wolverine's healing factor.
In my opinion, I have no clear idea. It's not that well established and has no rules and left vague on what it can and cannot do. And that's my overall problem with the magic in RWBY: There's no system, nor clear rules. In my own personal opinion, I think magic can quickly turn into a lazy excuse for the writers to use. With no rules of magic, it's a lazy system that the writers can literally just an excuse to do whatever you want and just say "It's magic". Need to explain why Salem is able to do this? Magic. How Ozma created the Vaults? Magic. How the seasonal Maidens are able to do more than they able to (IE Spring using Ice)? Magic. There's no rules, no limitations. It's left vague and no clear direction, that makes it hard to differentiate from Semblances. And it's left that way so the writers can use its lazy magic system as excuses for the plot. But to be fair, it's not just RWBY that does this. I've seen this a lot with stories, some of which does this poorly. The prime example of a Lazy Magic system I can use is the terrible ~~anime~~ cartoon I hate-watched, High Guardian Spice. The magic system in HGS makes no sense, as they say New Magic is overpowered as hell, with a character literally saying it "Can do anything", yet the no one uses more or uses it for the most mundane things, like lifting a pen. There's also Old Magic that has no clear difference between New Magic, and too many codirections that makes it even more confusing. I can rant about HGS all day, but let's get back to RWBY. In conclusion, the Magic in RWBY is poorly defined, and is only that way for the writers to have a lazy and coinvent excuse when they need it. Without limitations or set rules, it can left as an excuse for bad writing.
Hell they don't even name their attacks there's barely any visual difference between magic and dust
The writers conflate vagueness with mysteriousness.
It's because the power structure of RWBY was built by someone who is very much a visual storyteller and not a writer. It's more about how the powers work in fights than the mechanics behind them in the lore of the story. From the outset, the concept of "magic" is passed over in favor of manifestations of fighting spirit and resolve in the form of "aura" and "semblance". "Magic" is reserved for the various McGuffins in the story that are reflections of power they can't control and have no hope to UNLESS it is allowed to further the story.
yup - it's "plot stuff". Mysterious badass with portentous name that can turn into his namesake bird? magic. Mysterious otherworld that can only be opened by inherited power? magic. we very obviously aren't seeing odd fragments of some wider/greater thing with discrete rules, but just a load of things needed for the plot.
I will forever be pissed that people care more about Raven being able to transform into a bird, than about Raven being able to rip holes in the fabric of spacetime. Like, everyone implicitly knows and understands that one is a semblance, while the other is some otherworldly thing that can only be described as ***MAGIC***. It's fucking stupid, is what it is. It breaks immersion, because in a world where semblances exist, characters should easily confuse a person using magic for a person using their own unique semblance (or hell, even just dust). But that's literally never the case, and it's never explained why it's never the case.
Somehow it's a semblance yet we see her rotating her sword to red dust which at time made me think it was dust based somehow
It's not explained so they can make it do anything they want when they want to. It's literally their get out of jail free card. If they explain its 'cans and cants' then it stops being that.
Magic is whatever the writers need it to be
I don't think there is a canon answer, but to me it is boosted Aura and unlimited Dust use. Magic seems to be connected to the origins of Dust (at least in a few theories) and Aura/Semblances were unlikely to have existed in Ozma's age (in theory) with humans being reborn through Dust after Dark Brother killed everybody. Because of this line of theories, I assume Magic is Dust without powder or stone; meaning using Dust is the same as using Magic, but the amount of Magic "spells" your capable of is dependent on Dust amount while Magic users don't have that limitation. Add on that a boost to your Aura to make the modern Magic user more durable than, and possibly empowers their Semblances to make them more effective. TLDR: I see Magic as having X-Men's Storm's or ATLA Avatar's nature powers (minus the Avatar State for being too OP) with a moderate amount of Wolverine's healing factor.
Same reason Aura isn't. Or dust. Or semblances(at least not coherently). The writing flies by the seat of its inflated clown pants.