Other posts in this series: A Layman’s Guide to Functors in ReasonML Applicative functors I’ll start this post off with a tantalizing quote that I first heard from a former colleague/mentor Kris Nuttycombe: In functional programming, applicatives are the essence of parallel processing, and monads are the essence of sequential processing. In this post about applicative functors (aka applicatives), and my next planned post about monads, I hope to dig into this notion, and try to impart some intuition as to why this is true.