Dashboard
The dashboard is the page you land on after signing in. It counts what is in your account and gives you a way into each list.
The cards
Domain names. How many domains are in your portfolio, with a link to the full list.
Registrars. How many registrars you have recorded. This card also has an Onboard Registrar link, which is the same form as Add Registrar on the Registrars page.
Top level domains. How many endings your portfolio uses.
A card counts what exists. It does not tell you whether anything needs attention, so a healthy account and one with a broken provider connection look the same here.
What is not counted
Zones, DNS records and certificates have no card. They are read live through your provider connections rather than stored in your account, so there is no number to show until a connection answers.
Those areas are currently available to administrators only, so depending on your access level they may not appear in your navigation at all.