Hue is a web-based tool that lets you interact with CDH components to analyze and manipulate your data. You can also use Hue to build custom applications.
The Hue Server is a "container" web application that sits between your CDH installation and the browser. It hosts a suite of Hue applications and communicates with various servers that interface with CDH components.
The Hue Server uses a dedicated database to manage session, authentication, and Hue application data. For example, the Job Designer application stores job designs in the Hue database.
The Hue Server runs on a dedicated host, preferably within your CDH cluster, though it can be remote if the firewall is not overly restrictive. For small clusters of less than 10 hosts, the Hue Server can share a host with master daemons such as the NameNode. In a pseudo-distributed installation, the Hue Server runs on the same machine as the rest of your CDH services.