‘Higher-order functions’ is a fancy term for functions that take other functions as arguments or that return functions. Very powerful!

Techniques such as currying and memoization can both be expressed as higher-order functions. Aspect-oriented programming can also be achieved in JavaScript using higher-order functions.

D. A. S. Fraser, N. Reid, Jianrong Wu, Estimating Functions and Higher Order Significance, Lecture Notes-Monograph Series, Vol. 32, Selected Proceedings of the Symposium on Estimating Functions (1997) ...