R is a free, open-source software environment for statistical computing and visualization. R is also installed through CRAN and can be compiled and run on various UNIX platforms, Windows, and MacOS.
Rstudio is a popular interface that runs R code and can be install as an alternative to the R interface. Rstudio is an integrated development environment (IDE) that includes a console, syntax-highlighting editors, and various tools for plotting, debugging, workspace management, and history to make coding in R much easier and more intuitive. Rstudio is also open source and can run on Windows, Mac, and Linux.