RStudio Desktop is an R IDE that works with the version of R you have installed on your local Windows, Mac OS X, or Linux workstation. RStudio Desktop is a standalone desktop application that in no way requires or connects to RStudio Server.
RStudio Server is a Linux server application that provides a web browser based interface to the version of R running on the server. You may want RStudio Server to:
- access larger CPU and memory footprints
- leverage compute resources more efficiently
- control access to data in a centralized manner
- ensure the R package versions used are standardized
For more on RStudio see http://www.rstudio.com/products/rstudio/