Contact in DirectIQ contains the customer's personal data. Required information is an email. The first name, last name, date of birth and any other information can be stored optionally. One contact can be on different lists and used in different marketing campaigns.
Go to Contacts -> Contacts Overview to see how many new, subscribed and disabled contacts you have.
If you want to see the full contacts list, click New Contacts, All Subscribers or All Disabled. After that a page with a list of all contacts will open.