When you access a contact record (in Audience > Contacts), you have many details about that contact available.
Note: Don't forget email address is the unique identifier for contacts. Each contact will only have one email address.
If you click on Field Details in the contact record, you have many fields available.
All of these fields are attached to the shared, public contact record. This contact record is shared between any user group that has their contact label applied to this contact. Although you can upload data to any of these fields, you do not exclusively control the data in any of these fields. Anything you add to this part of the contact record can be overwritten by other users or data sources.
If you would need to upload your own data that is:
for customization or segmentation, you may want to create a custom data object or CDO. To find out more about CDOs or get a CDO created for your user group, please contact the Eloqua team.. If you have need the CDO worksheet, you can download it here.