Users and contacts are distinct entities in DFP Small Business.
Users are able to sign into your DFP Small Business account and use the application. The administrator for your account must create an account and assign a role to each user. All DFP Small Business users must have a Google Account.
Contacts are advertisers whom you've invited to view orders, line items, creatives, and reports for their campaigns. You can create a profile that contains contact information for each advertiser; when you save the profile, it sends an invitation to the contact. You can only enable a contact to view information for his or her own campaigns, and the contact will have read-only permission and cannot edit campaigns or reports. Advertisers that are invited to view their campaign information as contacts must have a Google Account in order to sign in and view their orders.