One of the special requisites to build web applications with Shiny is either the inclusion of, at least, the
UI.R files or the inclusion of
app.R, which should contain the equivalent codes of both
server.R. Shiny searches for these files to run the application.
UI.R stands for User Interface. In fact,
UI.R is the file where the different parts of the application's frontend (that is, what the end users see) is defined.
server.R, on the contrary, is the backend or the engine of the application, that is, where the data is processed.
As in any other web application, the Shiny-based applications have an underlying input-output concept where the user inserts information (input) and gets something ...