A monad is a descriptive term for certain objects with have certain properties. For example, a ring in algebraic theory is a set together with two operations (+

A monad is a descriptive term for certain objects with have certain properties. For example, a ring in algebraic theory is a set together with two operations (+ and ) with certain properties. The natural numbers (1,2,3,...) together with + being addition and being multiplication form a ring, but to say that 'the natural numbers were constructed as a ring' or that 'a ring is an abstraction for the natural numbers' is wrong. Both rings and natural numbers are descriptions of things which happen to fit. Similarly, category theory monads are a description of things with certain properties. These happen to be satisfied by IO actions in every language and Promises in JavaScript. Haskell allows you to define this abstraction within the language, but it is not the only language that allows this.