how does toCompVec exactly work?????

I tried to search so much about toCompVec, fromCompVec online.
But, I found nothing usefull.
So I am asking what does exaclty toCompVec and fromCompVec do????
I know how toComp and fromComp, it takes a vector(point as mathmatical representaion) and just see What is the visual equivilant vector in the other vector space(trying to explain intuitively without linear algebra details).
So what does toCompVec do exactly, in math language or after effects.
Thank you!