How to understand the difference in post/preprocessors in vacancies?

Question

Preprocessors

In vacancies they always write the same thing:
- less
- sass
- stylus
- postCSS
I don't understand employers, do they want me to know all these preprocessors or just one thing? And understanding people explain whether there is a difference which post / preprocessor I use?
For example: In development, can each participant write code in their favorite preprocessor, or is there any difference and it is IMPOSSIBLE to make everyone write in their own?

Answer 1

It's not higher mathematics. if you already know some kind of preprocessor, then mastering another one is a matter of several hours.
the collective farm is usually of no interest to anyone. therefore, it makes no sense to use several preprocessors at the same time.