There are two reasons for which Entrepreneurs are interested to create a web application.
First one, they want to solve their own problems. Like they want to manage customers (CRM= customer relationship management), want to manage their list of hundreds of products (Catalogue= product list), speed up their business processes (ERP= enterprise resource planning).
The second one, they want to solve others problem. Many online businesses and portals are the extensions of that. Some of the examples are Products Marketplace (Amazon, Flipkart), Business Directory (Yelp, Just Dial), Real Estate Marketplace (Zillow, Housing.com) and many more.
Next information is more technical. I’ll try my best to explain you in easy language.
The web application is made of two parts.
One is Frontend:
When user open website or web application in the browser. It load page with all its elements. What you see on the browser is web application frontend.
Frontend made up of web page layout and its elements like forms, buttons, sliders, page links etc. To create those visual things, web developer uses HTML and CSS.
I hope in past on web pages, you saw different effects like some forms automatically popups, display interactive google map, some objects on page blur out or new objects added on button click and many more.
The second part is Backend:
When the user feeds information and submits any form, search and filter for products on Amazon, login and logout from any website. That time you are getting some responses from the server in form of page content or list.
To provide you with this content (list of product) or complete that tasks (login, log out) some process happens at the server side. Those parts which user can not see but it works every time. This is called Backend.
It involves server-side scripting like PHP, Python, NodeJS etc.. Which process user action on the page and send a response in form of content.
Another important thing at backend is Database which is used to store information and data which collected from users and other resources. Oracle, MySQL is one of the most popular databases used worldwide.
I like to create an application because I can utilize my extensive knowledge in this web technology. I created many directory applications like Job portal, Hotel listing portal, Doctor listing portal, Real estate property listing portal etc…
Create different kind of marketplace web application are my favorite. I created a matrimonial marketplace, product marketplace etc…