Over the time, there are various forms in which a Hadoop application is defined. But in most of the cases there are following four core components of Hadoop application:
1. HDFS: This is the file system in which Hadoop data is stored. It is a distributed
file system with very high bandwidth.
2. Hadoop Common: This is common set of libraries and utilities used by Hadoop.
3. Hadoop MapReduce: This is based on MapReduce algorithm for providing large-scale data processing.
4. Hadoop YARN: This is used for resource management in a Hadoop cluster. It can also schedule tasks for users.