MapReduce is a processing technique to process large datasets with the parallel distributed algorithm on the cluster. MapReduce jobs are of two types. “Map” function is used to divide the query into multiple parts and then process the data at the node level. “Reduce’ function collects the result of “Map” function and then find the answer to the query. MapReduce is used to handle big data when coupled with HDFS. This coupling of HDFS and MapReduce is referred to as Hadoop.