Hadoop is an open-source framework for distributed storage and processing of large datasets across clusters of commodity hardware. It addresses problems with traditional systems like data growth, network/server failures, and high costs by allowing data to be stored in a distributed manner and processed in parallel. Hadoop has two main components - the Hadoop Distributed File System (HDFS) which provides high-throughput access to application data across servers, and the MapReduce programming model which processes large amounts of data in parallel by splitting work into map and reduce tasks.