It is important to note the differences between R and RStudio. R is a programming language used for statistical computing while RStudio uses the R language to develop statistical programs. In R, you can write a program and run the code independently of any other computer program. RStudio however, must be used alongside R in order to properly function. Often referred to as an IDE, or integrated development environment, RStudio allows users to develop and edit programs in R by supporting a large number of statistical packages, higher quality graphics, and the ability to manage your workspace.
R and RStudio are not separate versions of the same program, and cannot be substituted for one another. R may be used without RStudio, but RStudio may not be used without R.