Hadoop is a free, Java-based programming framework that supports the processing of large data sets in a distributed computing environment. It is part of the Apache project sponsored by the Apache Software Foundation.

Hadoop is a platform that provides both distributed storage and computational capabilities.

Hadoop was first conceived to fix a scalability issue that existed in Nutch, 2 an open source crawler and search engine.

            Figure: Hadoop Environment

Need for Using Hadoop:

Hadoop fills a gap in the market by effectively storing and providing computational capabilities over substantial amounts of data. It’s a distributed system made up of a distributed filesystem and it offers a way to parallelize and execute programs on a cluster of machines