The Dashboard is a configurable area for displaying content and usage data such as stats, task chart, links etc. Your Dashboard may be empty on first time use unless you have Rooms and content added by your Organisation administrator.
By default Dashboard will show rooms, tasks, files and activity in the content area on the left and stats widgets on the right.
You can customise the Dashboard with the 'Customize dashboard' link at the top right corner of the Dashboard page. Customisation will allow you to reorder the content widgets and change filter parameters for the type of Rooms, Tasks, Files and Activity you want to see on your Dashboard.
You can customise what is displayed in each item on the Dashboard with the link on the bottom right corner of each Widget labelled "Customize"