The Spring Framework is a powerful Java framework Includes a 
collection of programming and configuration models aimed at simplifying 
the development of Java-based applications and models aimed at simplifying the development of Java-based applications.
In other word Spring framework provides comprehensive infrastructure support for developing Java applications

Mentioned below are some of the modules can Significantly reduce the development time of an application.

• Spring JDBC
• Spring MVC
• Spring Security
• Spring Test

For example, we needed to write a lot of boilerplate code in the early days 
of Java web development to insert a record into a data source. However, by using the Spring JDBC Template, we can reduce it to a few lines of code with just a few configurations.

WHAT DOES THE SPRING FRAMEWORK DO?

• Allows programmers to concentrate on the business logic rather 
  putting more effort on configuration. 
• The key feature is the management of dependency, which provides 
  excellent interfacing with external frameworks by adding layers to them.
• Enables testing as it allows us to write decoupled code.
• Allows for inversion of control, through dependency injection.

What is Spring Boot?

Over the past few years, the Spring framework has become increasingly complex due to added functionality. To start a new Spring project, it requires a lengthy procedure.

Spring Boot was introduced to avoid starting from scratch and save time. This uses as a foundation the Spring framework.

In other words spring Boot is basically an extension of the Spring framework that 
eliminated the configurations of the boilerplate needed to set up a Spring application.

WHAT IS REACTJS?

React is a JavaScript library for building fast interactive user interfaces

WHY LEARN REACTJS?

• React is the most popular java script library
• There’s a ton of learning resources for ReactJS. 
• You can easily integrate React components into legacy code. 
• Components can be reused and can be nested for easy application composition. 
• The Virtual DOM is extremely efficient at rendering web applications
• It allows complex UIs to be composed from small and isolated 
  pieces of code called “components.”

NOW LETS CREATE A SIMPLE REACTJS!

Note: I suppose you’ve already set up a NodeJS environment.
Let’s install or update the latest version of npm first.

STEP : 1

First, we’re going to install a tool, Create React App, that will allow us to create our first React project, Open up your working directory in terminal and use the commands as follows:

>>mkdir titan_React_demo
>>npm i -g create-react-app ( create-react-app node package sets up the React project )

STEP : 2

Create your project

Navigate to the root directory of your project and create a new React 
project:

>>npx create-react-app first-react-app

STEP: 3

Awesome, you can start your project now

>>cd titan_React_demo 
>>npm start

Your default browser should launch automatically, and you should get a screen like this:

Firstly,What do we mean by Web services?

Web Services are client and server applications that communicate over the World Wide Web’s (WWW) Hypertext Transfer Protocol (HTTP). In other words its simply a ‘method’ or ‘function’ in a normal programming language, except you are calling it over the internet.

For example:
Lets say you are creating a website that shows weather information of cities. You can actually get the data for the cities for already exposed web services. You will get the response in form of XML or JSON, you can parse it and show it on your website.

Okay now what meant by RESTful web services?

A RESTful web application shows information about itself in the form of
resource information. It also allows the customer to take action on these
resources such as creating new resources (example- creating a new user) 
or changing existing resources through HTTP verbs

Resources – They describe the “things” that a client may want to pull from a server 
(e.g. documents and files that make up a web page).

HTTP verbs- Which are the web verbs — they describe the “actions” you can take on a resource, such as GET, POST, PUT, and DELETE.

Application program interface (API) – HTTP requests to GET, PUT, POST and DELETE data.

Now Lets Discuss what is express JS?

It is a web framework that allows you to structure a web application in a specific url to handle multiple different http requests. 

Express is a flexible framework for Node.js web apps designed to make it much easier to develop websites, web apps, and APIs.

Why use expressJS ?

Basically, You can use few lines of codes with express JS to do a complex task with ease and also supports multiple templating engines to simplify generating HTML.

example: Express helps you with route support to respond to requests so you can write responses to specific URLs

How to Install & use Express ?

You can simply get it through NPM as follows:

>>npm install express

WHAT IS NODEJS?

Node.js is a JavaScript, cross-platform and open source  framework or runtime environment built on the Google Chrome JavaScript V8 engine.