Big data refers to the massive amounts of unstructured data that are growing exponentially. Hadoop is an open-source framework that allows processing and storing large data sets across clusters of commodity hardware. It provides reliability and scalability through its distributed file system HDFS and MapReduce programming model. The Hadoop ecosystem includes components like Hive, Pig, HBase, Flume, Oozie, and Mahout that provide SQL-like queries, data flows, NoSQL capabilities, data ingestion, workflows, and machine learning. Microsoft integrates Hadoop with its BI and analytics tools to enable insights from diverse data sources.