I have a question please for professional. Code:

Question

Code:
<span style= --i:1;><span>

QUESTION
What (( style=--i:1;)) means in an easy way please.

The second one.
Code:
Rotate (calc( var())

THE QUESTION:
what var means here in a very easy answer.

Answer 1

rotate(), calc(), var() are css functions

https://developer.mozilla.org/en-US/docs/Web/CSS/transform-function/rotate()

https://developer.mozilla.org/en-US/docs/Web/CSS/calc()

https://developer.mozilla.org/en-US/docs/Web/CSS/var()

style= --i:1; are looking as custom property, but i am not sure.

This custom property are used together with var()
https://developer.mozilla.org/en-US/docs/Web/CSS/--*