• Node.js files include tasks that will be run in response to particular events.  
• A common occurrence is someone attempting to reach a server port.  
• Node.js files must be launched on the server before they may have any effect.  
• ".js" is the extension for Node.js files.

Think of modules as being equivalent to JavaScript libraries.
A set of functions that you want to include in your application.
To include a module, use the require() function with the name of the module:
var http = require('http');
Now your application has access to the HTTP module, and is able to create a server:
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/html'});
res.end('Hello World!');
}).listen(8080);

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Node.js is preferable for the following reasons:  

• Node.js is a lightning-fast programming language.  
• Node.js never waits for an API to deliver data, making it ideal for data-intensive, real-time web applications.
• Over 50,000 packages are accessible to developers through Node Package Manager.
• The same code base makes keeping the server and client's code in sync easier.
• Node.js is a JavaScript library, making it simple for web developers to utilize it in their initiatives.

Streams are objects that enable you to read data or write data continuously.
There are four types of streams:

• Readable – Used for reading operations
• Writable − Used for writing operations
• Duplex − Can be used for both reading and write operations
• Transform − A type of duplex stream where the output is computed based on input

HTTP defines a set of request methods used to perform desired actions. The request methods include:

• GET: Used to retrieve the data
• POST: Generally used to make a change in state or reactions on the server
• HEAD: Similar to the GET method, but asks for the response without the response body
• DELETE: Used to delete the predetermined resource

• Node.js can create dynamic page content.  
• Node.js can create, open, read, write, delete, and close server-based files.  
• Node.js can gather form data.  
• Node.js can insert, remove, and alter data in your database.