Hadoop is not an operating system but rather a framework for distributed computing that allows for the processing and storing of large data sets across clusters of computers. It is typically run on top of operating systems like Linux or Windows.

Hadoop’s core components include:

1. Hadoop Distributed File System (HDFS): A distributed file system that stores data across multiple machines, maintaining redundancy to ensure fault tolerance.
2. MapReduce: A programming model that allows for the parallel processing of large data sets.
3. YARN (Yet Another Resource Negotiator): A cluster management component that manages resources and schedules tasks.
4. Hadoop Common: The standard utilities that support the other Hadoop modules.

Several distributions of Hadoop exist, including ones from Apache, Cloudera, and Hortonworks. Many organizations utilize Hadoop to analyze and manage large amounts of data, massive data analytics.