MapReduce is a programming model implemented with a library for processing large datasets - often termed as BigData - on clusters of commodity computers. MapReduce is typically used for distributed processing of non-structured datasets. The map function processes key/value pairs and generates intermediate key/value pairs based on user specified map function. The reduce function merges and processes intermediate values belonging to the same key. A simple example of MapReduce will be shown on the open source software framework Apache Hadoop.