A manifesto is a public declaration of intentions, opinions, objectives, or motives, as one issued by a government, sovereign, or organization (http://www.dictionary.com/browse/manifesto).

The Reactive Manifesto clearly articulates the views of the issuer, following which an application can be developed to be reactive.

According to the Reactive Manifesto (https://www.reactivemanifesto.org/), a reactive system should be responsive, resilient, elastic, and message-driven.

Let's get into each of these terms in a bit more detail. Most of the text in this section is from the online Reactive Manifesto and then slightly modified to convey the concepts in more easily digestible terms for the readers.