．Hadoop is a software platform that lets one easily write and run applications that process vast amounts of data.
．Hadoop implements MapReduce, using the Hadoop Distributed File System (HDFS) MapReduce divides applications into many small blocks of work. HDFS creates multiple replicas of data blocks for reliability, placing them on compute nodes around the cluster. MapReduce can then process the data where it is located.
．Hadoop is a Lucene sub-project that contains the distributed computing platform that was formerly a part of Nutch.