OpenStack Dashboard (codenamed Horizon) is a graphical interface to manage OpenStack. It is a Django based web application that is very extensive and provides most of tools and information for managing your cloud.
Following image depicts how Dashboard is connected to all the components in OpenStack. Note that this image shows OpenStack with all the seven core components. Since, most of these are independent of each other, this configuration can vary to a great extent.
Hope it will help you.