What are Daemons in Hadoop and types of dameons

Daemons:
Daemons are resident programs which constitute to hadoop running. In computing terms it is a process that runs in the background.
Hadoop has five such daemons. They are 1.NameNode,
2.Secondary NameNode
3.DataNode
4.JobTracker
5.TaskTracker.

Each daemons runs separately in its own JVM. We discuss about these daemons in this post as they are associated with HDFS and MapReduce.