This document provides an overview of Hadoop MapReduce. It begins with an introduction to MapReduce and defines it as the processing component of Apache Hadoop that processes data in parallel across a distributed environment. The document then discusses two main advantages of MapReduce: 1) parallel processing, which makes data processing fast, and 2) data locality where processing is moved to the data rather than moving large amounts of data. It also provides an example of how MapReduce can be used to efficiently count words in a document by splitting the work across nodes and aggregating the results.