A software program that runs on a computer or smartphone.
Email programs, web browsers, games, and utilities are all applications. They are designed to carry out specific purposes.
Applications are how we interact in the digital world, especially with databases. Many applications are known as front ends, being tied to the servers which are collective called the back end. Here is where the data is stored pertaining to the application.
With the advent of Web 2.0, communication on the Internet became a two way street. As the applications are collected data, they are fed to the databases run by the corporations. Social media is a prime example of how this works.
For example, Twitter is a front end tied to a server system that is owned by the company of the same name. So the application is where the users engage, feeding the backend. This is what allows companies of this nature to mine the data and sell it to advertisers.
Web 3.0 promises to create a different structure for the Internet. Through the idea of decentralization, we can see how this model could change.
This uses the same front end/back end make. The difference is that, when blockchain is involved, the back end is the same for all applications tied to it. In other words, it reads the same data. Hence, each front is can decide what will show, can read and write to the network, yet has no ownership on the data. At the same time, accounts are accessed using a management system that is run by the chain.