Deffered and Method chaining

¿Qué es un Deferred?

Permite encadenar distintas acciones (callbacks) y disparar cierta funcionalidad (otros callbacks) dependiendo de su estado.
Tomado de: 

https://fernetjs.com/2012/02/entendiendo-deferreds-en-jquery/

Method chaining, also known as named parameter idiom, is a common syntax for invoking multiple method calls in object-oriented programming languages. Each method returns an object, allowing the calls to be chained together in a single statement without requiring variables to store the intermediate results.
Tomado de: 

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

En Jquery 
http://blog.mediumequalsmessage.com/promise-deferred-objects-in-javascript-pt1-theory-and-semantics