Computable function

https://en.wikipedia.org/wiki/Computable_function

Computable functions are the formalized analogue of algorithms, such that a function is computable if it can be implemented as an algorithm.

Particular models of computability that give rise to the set of computable functions are the Turing-computable functions and the μ-recursive functions.

According to the Church-Turing thesis, computable functions are exactly the functions that can be calculated using a mechanical calculation device given unlimited amounts of time and storage space.

Equivalently, this thesis states that a function is computable iff it has an algorithm, which here means a sequence of steps that a person with unlimited amount of time on their hands, paper and pencils, could follow.