A Board is a collection of widgets. Widgets may be linked to metrics organized across a user determined layout. Boards can be data driven dashboards or simple digital signage.
Boards contain widgets. A widget may be a chart, a number or simply a box to contain other widgets.
Each widget can also have a flow that contains the metrics for the widget to render. The flow is separate from the widget as it can be used on different widgets on different boards at the same time. Not all widgets have flows. For instance, most typical digital signage boards would be constructed from a flow-less image, video and text widgets.