A dashboard is a place where you can gather data from different boards. You can use this option for multiple purposes : 

• Get an overview of your different projects
• See your planning accross different projects
• See the global progression of a project that uses multiple boards to work
• Create a visually appealing report directly on monday.com

Dashboards are a really useful solution when you have to work accross multiple boards. Using widgets, you can create a report with the data you want to see and share : budget, timeline, workload...