How does this script work? (head movement with mouse)

Help and Feedback Scripting Support
#1

I want to know how this script works.
And why is it math.atan? I think it’s math.asin.

local TorsoLookVector = Torso.CFrame.lookVector
local HeadPosition = Head.CFrame.p
local Point = PlayerMouse.Hit
local Distance = (Head.CFrame.p - Point.Position).magnitude
local Difference = Point.Y - Head.CFrame.Y
Neck.C0 = Neck.C0:lerp(NeckOriginC0 * CFrame.Angles((math.atan(Difference / Distance) * 0.5), (((HeadPosition - Point.Position).Unit):Cross(TorsoLookVector)).Y * 1, 0), 0.5 / 2)