What am I looking at?
The diagram you can see here is a web view of the sample diagram, published through Visio Services. Using the controls at the top, you can change which section of the diagram you see, zoom in or out for a closer or wider view, and even see linked data sources through the shape information pane.
With Visio Services and either Visio Professional 2010 or Visio Premium 2010, you can publish any type of diagram (static or data-linked) to SharePoint, so others can view the diagram without needing to have Visio installed on their machines.