This document provides an overview of big data and Hadoop. It defines big data as large, complex datasets that are difficult to store and process using traditional systems. Examples of big data sources are listed. Hadoop is introduced as an open source framework for distributed processing of large datasets across commodity computers. Key components of Hadoop like HDFS for data storage and MapReduce for parallel processing are described. Reasons for moving to Hadoop include its ability to handle large, unstructured datasets across clusters of servers in a scalable way. The future of data growth and the Hadoop ecosystem are also discussed briefly.