API is an acronym for application programming interfaces and you can imagine it as a user interface application, but for software instead of humans. Saying it in another way, it could be seen as a tool for your programming. When you need it to insert a nail, you call a hammer API, and if you need it to remove a nail, then you call a plier API. Spark has its own toolbox API for R, which you can access here: https://spark.apache.org/docs/2.2.0/api/R/index.html.
Following our explanation, extensions are customized R packages created to provide an interface to any Spark package, or the Spark toolbox. There are many extensions already available, but you also can create your own extension to call any of these Spark APIs. One extension example is the rsparkling package viewed in the previous section; it is the rsparkling package that provides an...
