An R package is a related set of functions, help files, and data files that have been bundled together. At the time of writing this, Comprehensive R Archive Network (CRAN) (https://cran.r-project.org/) has over 12,000 packages available for R. This is a huge advantage when using R, since you don't have to reinvent the wheel to make use of very high quality packages that probably implement the functionality you're looking for, and if there aren't any such packages, you can contribute your own!
Even if CRAN doesn't have a package with the functionality you need, it may exist in personal Git repositories in GitLab, GitHub, Bitbucket, and other Git hosting websites. As a matter of fact, two of the packages we ...
