What is the difference: first class functions and higher order functions?

Question

JavaScript

In programming languages ​​there are such concepts as: first-class functions - first class functions , higher order functions - higher order functions .
After reading the definitions, it is not clear what is the difference, or are they synonyms?

Answer 1

Higher-order functions are functions that can take other functions and return functions. first-class functions is a language feature that allows variables to contain function references. In fact, they are different things, but separately there is not much sense in them :)