What is opening a channel?

[Alila]

Hi,
Here I am, asking more annoying questions. ;)
Could I know what is happening when you open a channel--hydromancy, cryomancy, or so forth? I've tried to do my homework: channeling is the wilpower component for any kind of magic, but the mancy is...for elemancy maybe it's holding that pattern in your mind's eye? But what is it for sorcery, cryomancy, or thaumaturgy?
More specifically, is there a lore specific reason for the visual effects and why they always seem to be focused around the hands? Even aeromancy has one, even if it's super sneaky stealthy for everyone else!
Oh wait, thaumaturgy seems to be a halo. Oopsies :D
Okay, so for the most part the visual manifestation of an open channel seems to be centered around the hands. Why is that, and why do they happen in the first place?
If the answer is "because it looks pretty" that's an entirely valid reason, but everything on Clok seems to have lore and...
I will be honest--I was considering being selfish and requesting a donator thingy next month and I wanted to make sure the request didn't break any non-obvious lore-ly things. Don't judge me too harshly pleasy :(
Also on my archeological dig there were these old posts about channeling instead making your hands glow with pretty colors. Was this changed for the current messages because they are more in line with what magic should be?
And one last thing--have magical flourishes ever been considered?
Sorry for the all-over-the-place-ness of the post, and thank you for pushing through!
Thank you,
-Alila
;)