So, assuming that you have a fair idea about what Spark is and the basics of RDDs. Paired RDD is one of the kinds of RDDs. These RDDs contain the key/value pairs of data. Pair RDDs are a useful building block in many programs, as they expose operations that allow you to act on each key in parallel or regroup data across the network. For example, pair RDDs have a reduceByKey() method that can aggregate data separately for each key, and a join() method that can merge two RDDs together by grouping elements with the same key.
When datasets are described in terms of key/value pairs, it is common to want to aggregate statistics across all elements with the same key.
Paired RDDs bring us back to that key-value pair paradigm which Hadoop’s version of MapReduce brought to the forefront.