What is a monad? — In functional programming, monads are a way to build computer programs by joining simple components in predictable and robust ways. A monad is a structure that represents computations defined as sequences of steps: a type with a monad structure defines what it means to chain operations together, or nest functions of that type. This allows the programmer to build pipelines that process data in a series of steps (i.e. a series of actions applied to the data), in which each action is decorated with additional processing rules provided by the monad. A monad is defined by a return operator that creates values, and a bind operator used to link the actions in the pipeline.