If you are a starter of shiny as me, this post may help your know some principle of shiny.

What is shiny?

Backgroud needed

Reactive Programming

When the input changes, the R code will run again to get a refresh. Shiny makes the connections among R, input and the the output on your screen by some communication tags. So you can just focused on R code and let shiny do the other things.
server.R

You need write your R code here to tell shiny run what when the inputs change. The R code need a input and output values.
ui.R

You need tell the app user where is the input/output box, which values of the input should be transfer to R code and which values of the output should be display on the webpage. You can also custome your UI of app here if you have writen some basic html pages.
Render function in server.R

Tell shiny the output values used in the app’s webpage. This function need to be re-ran when the input changes, so the render function must be assighed to a output values while contains the input values.
RUN

When you finish your server.R and ui.R, just runApp() and you will get the great webpage.

Push your shiny code on the github or make a zip file, the user can run it locally use the runUrl,runGitHub or runGist in the shiny package.
You can also build up a server with www connection and put your app there.