This document provides an overview of Big Data and Hadoop. It discusses how companies are generating large amounts of data daily. Hadoop was created to handle such large volumes of data across clusters of commodity hardware. Key aspects of Hadoop covered include its history, architecture, ability to scale out across clusters, and ability to process data in parallel across nodes. Hadoop also aims to abstract complexity and handle failures which are common given the large number of machines in clusters. The document compares Hadoop to relational databases and explains how Hadoop is better suited to semi-structured and unstructured data.