What is the difference between CSS variables and preprocessor variables?

By Stephen Downes - Stephen's Web. What is the difference between CSS variables and preprocessor variables?
Chris Coyier, CSS Tricks, 2016/10/26
The world of web page style has become complicated and complex, partially because of the need to support numerous browsers (both PC based and mobile) and partially because large-scale projects require variables and functions to facilitate management. More...