Go to Dashboards Tab and select proper item (2) in top right menu button (1):

The Planning Dashboard contains following elements:

• Filters selector (3) allows to switch between pre-defined and custom filters, grouping and sorting orders
• Subheader (4) shows currently applied grouping and sorting order
• "Group By" button (5) will show submenu that allows user to select necessary field to group tasks by it
• "Filters" button (6) toggles "Filters" sidebar that allows to set up and manage filters
• "Show Gantt" button (7) toggles Gantt chart of the dashboard (see proper section below about Gantt chart)
• "Refresh" button (8) reloads dashboard data

Tasks on the Planning Dashboard are shown as table with several columns (9) containing most important task properties. These columns are sortable, so steps can be shown in necessary order.

All tasks are grouped together by default and can be grouped by other fields. Groups can be collapsed or expanded using proper togglers (10). Each group has a badge showing amount of entries in it (11).

Each task allows to open a process diagram (12) and Gantt chart (13) by clicking on entry menu items. Also each task contain links to proper process details page (14) and record details page (15).

The task (step) name link (16) shows a popup (see Step Properties section below) with step details and buttons to manipulate with step.

Each step has a left border which color represents a step status (17): green is complete, yellow is active, blue is future step.

"Load more" button (18) allows to show more steps.

If click on step name link (16), a popup (19) will be shown.

For future (blue-bordered) steps popup will show only some basic properties (if they are set for this step):

For completed (green-bordered) steps popup will show the same step details (General, Assignee, Layout, Checklist, Time, Tasks/Issues, Data, History Details, etc. - corresponding to tabs allowed to show for this step in it's properties set at Process Builder) as on the proper part of Progress Component at the Process Details page, but in read-only mode:

For active (yellow-bordered) steps popup will show the step details too, but allows to modify and save them (accordingly to current user permissions) - so, this popup repeat functionality of the proper part of Progress Component at the Process Details page and also allows to proceed (approve, reject) steps:

User can display the Gantt chart for all currently shown steps on the Planning Dashboard by clicking button (6). The Gantt chart will be shown at the right side (20). It will show proper step dates and durations graphically (21).  

In Gantt mode all other dashboard and steps functions and properties are still available.