Hadoop is a framework for distributed computation and storage of large data sets on computer clusters, developed by Apache Hadoop. It consists of three core components: HDFS (Hadoop Distributed File System), MapReduce, and YARN (Yet Another Resource Negotiator). HDFS provides scalable and fault-tolerant data storage, while MapReduce is a framework for processing large datasets in a distributed fashion across multiple machines. YARN manages the allocation of computational resources for MapReduce jobs. ZooKeeper is used for coordination and synchronization of distributed systems, enabling high-availability of HDFS and YARN components. Understanding how these technologies work together is crucial for monitoring Hadoop health and performance.