In R, the fundamental unit of share-able code is the package. A package bundles together code, data, documentation, and tests, and is easy to share with others. There are currently over 13,000 packages available on the Comprehensive R Archive Network, or CRAN, the public clearing house for R packages. This huge variety of packages is one of the reasons that R is so successful: the chances are that someone has already solved a problem that you’re working on, and you can benefit from their work by downloading their package. Packages thus allow for easy, transparent and cross-platform extension of the R base system.
Packages can also depend on other packages as stated in the fields
Suggests in each package’s meta data file
DESCRIPTION. Through their dependencies packages can span a huge graph which is also referred as an entire Package Universe. Below you can find an example graph including the most downloaded packages on the RStudio CRAN mirror: