What are the various options in dashboard?

Your personal dashboard consists of dash-lets that allow you to track all information relevant to you. The first thing that you see after you login is your personal dashboard.

The default setting shows you a list of below mentioned dash-lets:-

My Departments - My Department dash-let displays all departments that you have created or of which you are a member. Use this dash-let to create new and delete existing department (Note- Department can be created or deleted only by System Administrator). You can also enter a department from this dash-let.
My Activities - My Activities dash-let tracks the most recent activities that have been performed in any department of which you are a member.
My Tasks - The My Tasks dash-let displays the incomplete tasks assigned to you and invitations to join departments.
My Documents - The My Documents dash-let enables you to view files from all Document Libraries that may be of particular interest to you, organized into three categories: Favorites, I'm Editing, and I've Modified.