Visualizations help you to understand your own XenServer infrastructure, to correlate event and detect bottlenecks.
The dashboard is a view gathering information on all your connected pools/hosts.
You can also update all your hosts (install missing patches) from this place.
A Parallel Coordinates visualization helps a lot to detect proportions in a hierarchical environment. In a XenServer environment, it's especially useful if you seek information in a large amount of data.