This document provides an overview of the Hadoop framework. It describes the key components of Hadoop including the NameNode, DataNodes, JobTracker, TaskTracker, and SecondaryNameNode. The NameNode manages the file system metadata and data locations. DataNodes store the actual data blocks. The JobTracker manages jobs and schedules tasks on TaskTrackers running on slave nodes. The SecondaryNameNode assists the NameNode in the event of failure. Hadoop uses a master-slave architecture with the NameNode and JobTracker on the master and DataNodes and TaskTrackers on slave nodes.