What Is Express JS?     

Express is a node js web application framework that provides broad features for building web and mobile applications. It is used to build a single page, multipage, and hybrid web application.

It's a layer built on the top of the Node js that helps manage servers and routes.

Why Express JS?

• Express was created to make APIs and web applications with ease,
• It saves a lot of coding time almost by half and still makes web and 
• mobile applications are efficient.
• Another reason for using express is that it is written in javascript as javascript is an easy language even if you don't have a previous
• knowledge of any language. Express lets so many new developers enter the field of web development.

The reason behind creating an express framework for node js is:

• Time-efficient
• Fast 
• Economical
• Easy to learn
• Asynchronous