What is difference between Action and Transformation in Spark?

[Ryan_Chynoweth · Accepted solution]

An Action in Spark is any operation that does not return an RDD. Evaluation is executed when an action is taken. Actions trigger the scheduler, which build a directed acyclic graph (DAG) as a plan of execution. The plan of execution is created by working backward to define the series of steps required to produce the final distributed dataset (each Partition). A transformation are functions that return another RDD.