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 DataNodes store the actual data blocks. The JobTracker is responsible for scheduling jobs across the cluster and TaskTrackers execute tasks on slave nodes. The SecondaryNameNode provides backup support in case of NameNode failure. Hadoop uses a MapReduce programming model where data is processed in parallel across clusters.