The Shiny web framework fundamentally enables collecting input values from a web page, making those inputs easily available to the application in R, and having the results of the R code written as output values to the web page. In its simplest form, a Shiny application requires a server function to do the calculations and a user interface. Shiny applications have two components, a user-interface definition and a server script.
Source: R Studio
Shiny comes with a reactive programming library that you use to structure your application logic. By using this library, changing input values will naturally cause the right parts of your R code to be re-executed, which will in turn cause any changed outputs to be updated. The reactive programming model eliminates the need for additional event handling code.
In Shiny, there are three kinds of objects in reactive programming: reactive sources, reactive endpoints, and reactive conductors.
You can install Shiny the usual way from your R console: