The Config tab is used to edit the following files:
server.xml web.xml context.xml tomcat-users.xml setenv.sh
These files can, of course, be edited via the file system or VI as well.
The Java tab is used during installation as well as for updating of JDK.
It can also be used to un-install the selected JDK and replace it with a new version.
When installing or removing, there is an option to set as System default.