Host Manager is a web application inside of Tomcat that creates/removes Virtual Hosts within Tomcat.
A Virtual Host allows you to define multiple hostnames on a single server, so you can use the same server to handles requests to, for example,
Unfortunately documentation on the GUI side of the Host Manager doesn't appear to exist, but documentation on configuring the virtual hosts manually in
context.xml is here:
The full explanation of the
Host parameters you can find here: